for me it would be a z400, but thats just me, everyone has different opinions, some may like the yfz or 450 r more.
but remember he said hes low on cash so the z400 is out of the qestion considering you have to dump alot of money into the engine in order for it to keep up with the 450's.
i would say either of the 450's its up to you what ever one you like.
well not really, two of my friends raced the other day, one with an 04 yfz with a full system sparks, and a z with nothing but a 16 tooth sprocket, the yfz killed the z in take off, but since it was a long road, the z pulled away and won by a bike, but since youll almost never reack top speed on a track, i guess youre right.