Bt200x, ct200u-ex Pros and Cons. Mini bike suggestions?

I would like to buy a mini bike for $600 or under. Any suggestions?
I don't want a little 2.5 -3.5 mini bike. I want a 6.5 or abouts.
Thank you,
These are the same mechanically.They have totally different riding positions..the bt is more upright so should be a more comfortable rider imo
Yes. I plan to do two mods, first take out throttle screw. then switch out crankshaft for 3/4 inch one and put a tav 2 on.
I hear they get up to about 45 MPH with theses mods done.
Thanks for replying all.