Big Bore vs. Stroker

Just kicking the idea around a little. Got to go through the crf450r this winter (now). I noticed Hot Rods has a 3mm stroker that can use stock piston for not much more than a standard crank. Lots big bore kits out there. Just wonder what to expect from one or the other? Will either one be dependable. My son seems to like the power down low and mid but would like a little more up top.

Thats what I wanted know, thanks. I may just go back stock because I have all my parts already except for a crankshalf. I have had them for awhile. Are there any modifications needed for the head on the big bore?