I'm booked in with the in-laws all bloody weekend so will have to wait until the following to play!
I haven't played MH since the WiiU but am pretty sure weight doesn't play a factor. Big weapons are slow and small ones nippy. It's the movesets that make things interesting - think the Souls games but more varied and involved. The long sword, for example, has a move that's a short dash and a swipe. Time it right as a monster lurches at you and you side step and whack it in the face. It looks and feels great. Likewise with the massive weapons that you can charge up. Unless you're familiar with the enemy you stand a good chance of getting trampled while charging up, but once you get to know how they behave - one might always pause after jumping - and you can time it just right. How monsters behave can also change mid fight. Damage might cause them to get slower, angry, call for help etc which opens up new/different opportunities. It's the combination of all this plus the different weapons that I like most about the combat. I'll stop now before typing myself into a hype frenzy