A 2stroke forum might not be the best place to ask about replacing one with a 4stroke, you are sure to get bias answers mostly with little to no facts.
First off the warrior and blaster last time i checked both do about 60mph stock, a google search will suggest the warrior is slightly faster top speed and you have the obvious problem of not being able to keep that 2stroke pinned and going balls out without blowing it up. Yes the blaster is faster off the line but that doesnt mean a warrior doesnt have some balls. Yamaha puts the same motor in a few other quads including the 350 raptor and i believe 350 grizzly? im sure somebody will correct me if im wrong, point is its a very proven motor And you wont have a hard time finding parts if need be.
It really comes down to where and how your riding. If you want to constantly beat your buddies off the line the blaster is better. If you want a extremely reliable trail quad that goes much farther on one tank of gas and wont have heat issues the warrior is better all day.
Before you blaster boys start bashing please know i have a warrior, blaster, banshee, and a 1988 lt250r as well as a handful of dirt bikes. I ride them all but as i said if im going out on the trails the warrior is always a better choice for me its proven to be the most reliable.