Help me choose a trials bike

Im a novice trials rider. Ive got a 300TXT GG. Its a lot of bike for a novice,  but has its positives at times. 

If its slippy mud, I can lug a bigger gear with lower revs. 
However I feel that when I want to 'launch' at something, Id be far more in control on a 200cc. 

Ive made mods to make my 300 'softer' and easier to ride, such as a low compression head (When I bought it it was an ex-expert rider's bike so had a high-comp head) and a slow turn domino throttle. Its much better suited to my ability with these mods. 

I occasionally have a ride on my mates 250 sherco & his teenage son's 125 sherco, which is a beautiful piece of kit when winding around the tight trees, but down on power to pull me (also 90kgs) up slow, steep climbs and not enough punch to launch at stuff.
If I was buying again, I think id get a 250. 

The 23 gasgas is a great bike and simple (carb and kick start) as is the beta.  The beta is probably a tad more novice-friendly.  The trs is a great bike and quite similar to the gasgas, but has the option of electric start.  The vertigo has efi and very high performance.  Reports of troubles are common and a top notch local dealer would be important.  The Montesa / Honda is a four stroke and extremely well built with top notch quality and suspension.  It's heavier than the others and most people prefer two strokes in trials so it has never been dominant.

For riding at or near sea level I'd suggest a 200-250.  Easier to ride and more performance than you'll need for a long time.  If at very high altitude I'd do a 300 to get some grunt back.

We have a few.

I'm on a Sherco 250 Factory (2018), absolutely love this bike. Power is fine, they don't make near the power or have the "power band" a dirt bike 2T does. 

My wife is on a Montesa 260 and father on a Montesa 300. 

The Montesa's, to me, feel fat on the front end, just like the gas gas.  My wife and father love these things, I personally don't see the fascination but we have more Montesa riders than not in our area (very small pool of riders). Before the Montesa's, my father had a Beta 300 Evo 4T for a year or so, can't recall what led him to get rid of it, but it didn't age well from what I recall. I'm not sure why, I'm not a fan of the Beta's, but greatly enjoy my 300RE. They do have excellent customer service.

The kicker on the gas gas is "unique" and the only local rider with one is selling it to buy a Montesa because of it. 

Gas Gas, the brand, has a history where I believe parts on relatively recent years can be a pain in the rear. Because of that, I've never really entertained one along with their goofy kicker is not appealing. Have a few friends that have these and they have their following.

End of the day, you can't probably go wrong with about any. I'd recommend finding the local club and trying a few out first before buying

GG, Sherco or Beta are simple and reliable. The Vertigo is more complex but better. The Honda Montesa is too much bike for anyone less than a good intermediate. And lastly the TRS has electric start as an option. It might be the best bike for the more advanced. 
 A Beta or Vertigo 200 would be my choice

If you can find an early 2000's Montesa 315R, I'd recommend that. I think anyone starting out on trials should start with a 2 stroke. I had a 2001 Dougie Lampkin edition. One of the funnest bikes I've ever had. You don't need a lot of space to have a blast. 

Find your local trials scene and figure out what dealers you have in your area, and what kind of support (parts availability, support at local events if you plan on competing) is around. Get to a local trial and look at the bikes, ask questions, maybe you’ll find someone who will let you ride theirs around a little bit, or dealers with demos. Generally, trials riders are extremely friendly and willing to help out others interested in getting into the sport. Much more so than in the MX/offroad worlds.

I’ve seen time and time again; folks who ride big bikes get a trials bike and go ride it around by themselves or with their big bike friend who also gets one. There is a huge difference between riding around on a trials bike, and getting together with actual trials riders and learning HOW to ride trials. It is extremely humbling at first, and frankly most people who have been riding dirt bikes for years can’t handle the aspect of “starting over.” Just keep an open mind and enjoy the learning process. It’s truly one of the most enjoyable things you can do on a motorcycle.

Also, you’ll get way better advice over at Trials Central than here at Vital.  
 

Ossa

I started riding trials 3 years ago and bought a new GasGas TXT 300 as my first bike and was very happy with it. The TXT seemed very docile and easy to ride, compared to the bike I'm on now which is a Vertigo Nitro 300, which is a bit more exciting. 300cc two strokes have a lot of torque for effortless hill climbs and are easy to find and sell here in the USA anyway. I think it's probably the option for a guy your size, and you probably want to get stiffer springs at your weight. If you are in England it's probably easy for you to get parts from any bike you get than it is here. They all have their quirks in their designs. If you are buying used make sure you get the brakes, clutch, and tires in good condition. You will put yourself at a serious learning disadvantage if you are riding a bike with poorly performing brakes, for example. 

I use my trials bike for single track. All I can say is any trials bike is good, all the reputable brands have been out for a while and you really can't go wrong with any of them.

Beta, GasGas, Vertigo, Sherco, Honda all great bikes. The real decision lies in the power package you choose. 2 stroke/4 stroke, 125/250/300.

I'm a lighter weight rider 138lbs and I like my 300. Yeah it does all the hill climbs, endless torque, etc etc. What really set the 300 apart is in the transfer gears 5/6th. The motor is strong enough to provide good top speed and not bog down dramatically because the taller gear ratio.

A 300 will also tow your buddies to safety easier.

Montesa Honda.          300cc and 260cc EFI Batteryless.

https://powersports.honda.com/motorcycle/montesatrials/montesa-cota-4rt…

I run a Trials riding school in Southern California called MotoVentures. Look us up on Instagram or Facebook (shameless social media plug)

In my opinion, the Montessa 4-strokes are good for learning (I have a bunch of them, they are good rental bikes, 260cc is the easiest to ride).

GasGas 2-stroke 300 is my "race bike".

A 200-250cc 2-stroke is good for novice trials riders, but vet experts ride the 300 2-stroke.

Montessa (Honda) and GasGas (KTM) have the best dealer network, easier to find spare parts/ aftermarket parts and sometimes you can find better deals on them (because there's more of them out in the marketplace). Beta is a close third with dealer network and parts, etc.

The American National Champ rides a Sherco, so there's that.

Vertigo has some cool technology.

There's Electric Motion with the E-Trials bikes! They are super fun but aren't as capable as gas powered trials bikes.

Any trials bike you get you will be stoked! They are so much fun and will definitely help your slow speed/ technical riding.

Hope this helps!

I have had some trials bikes over the years. went to the World Trial event in Montour Falls NY in 1999. Mind immediately blown... Bought a 1999 Beta Techno a few days later. I love trials riding, but you need to be in some trials friendly terrain. I don't have any trials appropriate terrain close to my home anymore, and do not have a bike at the moment. If I ever move into the mountains or anywhere with rugged terrain, trials bike is #1 on the list.