yfz 450 all the way ,,,, stock for stock the yfz has the hardest punch when it comes to power, great tranny, the 5 valve set up is the most reliable i think . i have owed 2 trx450r's there great all around, get the head ported and it will wake up, it also has a better head design than the yfz better makes better over all peak hp when modified than the yfz but not torque . I've owed 1 ltr , like stated above it has a shit tranny, and the stock valves suck i ended up dropping a valve , replaces all 4 new and 40 hours later happened again, EFI is nice tho. just my 0.02 cents