I haven't seen the June DB, but the May issue has a shootout iwth the KTM the clear winner. Quoting DB, "the Yamaha finishes a not-so-close second".
I just recently bought a 450 EXC and love it. I had been away from dirt bikes for several years and worried the 450 would be too much bike to get back with. No problems. It's a sweet bike. I love the torque. I weigh 215 and think the 250 would be a little light in the torque department. I also ride the WV hills as I live right in the middle of the Hatfield McCoy system. The 450 is heavier than the 250, but it feels very light compared with the XRs and DRs I've ridden. I don't think you could go wrong with either bike, but like an earlier post said, you'll end up wanting more power, messing with pipes, cams, etc. The 450 already has the juice, even with the stock pipe, which is relatively quiet. I've had bikes I couldn't start in the driveway at night becauses the noises pissed off the neighbors. No problem with this bike.