250 2t vs 350 vs 450

I am a two stroke die hard and ride a YZ 250. Had the chance to throw a leg over a 2024 KX 450. My last four stroke was a 2012 KX 450, which I rode (and hated) till 2018, and then I have only ridden my 250 two stroke.

My YZ doesn't hold a candle in any aspect to the new KX. The traction control and power modes make it super easy to ride, handles awesome, corners great, suspension right out of the box is very good. It is insanely easy to grip the KX with your legs, the contact points are absolutely perfect and it is nothing like my 2012 was in any way. The terrible engine braking big thumpers used to have back in the day isn't there anymore.

But I still choose my YZ. I cannot explain how much better of a rider this bike has made me, and although I would be seconds a lap faster on the new 450, I feel the two stroke is still helping me become a better rider. Although the 250 is aggressive, it is lighter and less powerful than a brand new 450. It helps that I only ride motocross for fun, and don't race.

To answer your question, the 350 might be the ultimate motocross bike. You won't regret it, and certainly won't miss the two stroke.

A YZ250 would be a great second bike if you like a 250 two stroke.

The 2022 KTM two strokes with some jetting work are superior to the new injected models.
After riding the 2023 TC125 and TC250, you can pry my carburetors from my cold, dead hands.
I haven't ridden an aftermarket ECU on the newer Austrian two strokes,  Maybe that would change my opinion?

I'd like to reference Randy Richardson, the Teenior Citizen himself:

If you care about good times over lap times, get a 2T. I've spent a lot of time on all three (450, 350 and 2T). I went back to a KTM FI 2T when they came out in 23 and I'm enjoying riding more than I ever have...even if I'm a second or two slower every lap...and have a harder time getting a good start. I'm 50 and really don't care that much if I finish 5th instead of 3rd. I just want the day to be about fun and IMHO, nothing is more fun than a new KTM 250 2T.

i Have a YZ250F and a 2009 KTM 150SX i restored recently.  I am 190lbs without gear and I ride the 1 fiddy almost exclusively now. I love how that thing just rips up corners and screams. But im an old school 2T ride also. I like the YZ 4T , but i find myself jumping on the KTM every time lately. 

I'm fortunate to have one of every displacement (at the moment).  Some thoughts:

150: Fun, but harder to ride fast.

250 2-T: Fun, fast, and handful if not ridden regularly.

350: Almost just right, not too slow, not too fast.

450: torquey, responsive, easy to ride fast.

A well setup 350 is hard to beat for a non-pro race bike.  A well setup 250 2-T is more fun to ride, but harder to race.  

Some good info in here. After selling my 2022 ktm sx 250 and going to a 2022 gg mc 450 it hasn't been everything I hoped a 4 stroke would be. It's a great bike, very reliable,  has smooth awesome power, etc. But I have always had trouble cornering with this bike, always feels like it wants the outside line compared to my 250 smoker, I have no way to prove this but I feel like I'm a slower rider on the 450. Highly considering going to a 350, but am afraid I'll miss that 450 power. As it has made me a better jumper due to the point and shoot power, you always have enough power to jump anything you feel comfortable attempting, never had that type of comfort/confidence before. 

That statement makes me wonder about your chassis setup...   The 450F chassis turns well when it's dialed in.

Do you have your sag set properly?   Too much sag causes a bike to turn poorly.
Have you tried playing with fork height?   

I find that I like the 2nd line on the fork tube (5mm of tube above the clamp) is best with 104mm of sag on the 2022 KTM chassis.
Some guys like less sag (102mm) or the 3rd line on the fork tubes...

Those are all worth a try before you give up on the bike.

Other things to think about are that too much air pressure in the air fork and/or a combination of too much compression with too little rebound could cause the fork to ride high in the stroke.   Less air and less compression will allow the bike to settle into a corner more easily.  More rebound will keep the bike turning a bit longer while you roll the throttle on from apex to corner exit.

I've ridden the 3 Austrian bikes. 21' FC350, 22' MC450f, and my 21' TC 250.

I prefer my own 250. It's just lighter and easier to  manage. I'm 5'7 135 so it fits my size well.

Next would be the 450. I like the power and being able to rev out and still feel the bike accelerating hard.

350 was good just not my flavor. I could tell it was down on power compared to the other 2 bikes. Ergos were great tho.

This is crazy...    I rode both my YZ250, then my MC350F back to back on Thursday at a track I built a month ago for some friends.

Both bikes are set up pretty well at this point.
I was two seconds faster on the 250 than I was on the 350 according to my Garmin GPS watch and a private Strava segment I have for that location...  

I didn't jump the three in the two-three section on the YZ250 and it was still faster on my two best laps than on the two best laps of the 350F.   I assume this is because the four stroke lets me trail ride around like an old man while the YZ250 forces me to be on the gas or roll everything.   Still, it made me laugh a little bit.   

Got a chance to ride my first yz250 yesterday and I honestly loved it. No way would I be as quick as my 350 or 450 but it would definitely by an amazing 2nd/training bike. 

Rode 350 and 450 on the same day and I've decided 450 is going. 350 was quicker/safer and easier to ride longer. Might swap 450 for a yz250, I think 350sxf and yz250 would make a very sweet combo.