Save yourslef the hassle and get the yz450f. I have always loved yamahas, and I took a long break and then decided to get a yz250 this past summer. It was alot of fun until I rode a yz250f and then a 450. I didn't want to go back to the yz250 or any two stroke, so I bought a yz450 and later sold my 250.
I rode an 02, 03, and 04 CRF450 and the 03 yz450...my conclusion was the yz450f. The CRF and YZF are both really great. The yz just felt more comfortable for me being 6'2". I ride mostly supercross and motocross and I found that I can pretty much stay in 2nd gear for the whole track, wheras on a few larger triples my friend with an 04CRF has to upshift to 3rd-sometimes he complains about having to be between gears?? (in case you didn't know the yzf has a 4 gear transmission and the CRF has 5) I never even come close to needing 4th gear on the tracks I ride.
Hope this helps in your search for the right bike.