Honestly, do a practice cut and try it out. If you feel good afterward and feel it's necessary, then go for it. Otherwise, I wouldn't even bother cutting unless you feel a vast strength disadvantage against other guys at 135, and there's no point cutting if you can't make a healthy cut. Also, become as lean as possible if you do cut to 125. Having to cut less water is better, because after dehydrating to a certain point, some of that water is coming out of your head. That's less cushioning for your brain during the fight. Faber talks about it a bit on the JRE.