Whenever I move up, I usually just buy in full. It never really occured to me to buy in half. I think if you are comfortable playing with 100BB, you shouldn't through yourself off your game by playing with a smaller stack. The logical reason I could see for buying in short would be if you're playing scared. Like if losing $50 in one hand makes you weezy, buying in for less is alright I guess.

IMO, you should just play with whatever feels most comfortable. You are in no danger of going busto, and if you drop a couple buyins, so what. You know you can handily beat 25NL, so I recommend you give it a real shot.