We take all our gear (BC/fins/booties/reg/mask/backup computer/assorted lights/mesh bags/lots of assorted little stuff.) If I have room and depending where we're going, I may take an extra reg or other spare stuff. We only wear 1mm skins, so that helps, although we often each take 2 along as it's nice to have a fairly dry one to put on. My husband takes a bunch of camera gear (housed DSLR, 2 ports, 2 strobes, lenses, arms, focus light, and all the little stuff that goes with it.)
I look at everything that goes in the bags (dive gear and not) and ask if we will actually use it this trip. I'm always trying to pare down because it all adds up, and I pay attention to weight when purchasing gear where it's more significant. I wouldn't buy a new reg just to save a couple pounds, but when we decided to buy new regs we went with lighter ones. Fortunately the fins we like are pretty light, but if they were heavy I'd be looking at that. My save-a-dive type stuff is in a couple soft zipper cases instead of a dry box, and I toss these in a drybag when it makes sense. A while back I bought a lightweight new drybag specifically for travel, since I was always forgetting to dig one out of the kayak when it came time to pack (despite the list), and the old bags were heavy anyway.
To minimize battery weight, I have mostly changed over first to LED lights and then to rechargeable batteries. My husband is taking a charger for strobe batteries anyway. For lights that take Cs I use AA adapters. So I'm taking smaller and fewer batteries than in the past.
Books used to contribute to our load; tablets and Kindles take care of that.
I try not to take too many clothes; I still take too many, but I'm getting much better. Besides a list of stuff to take, I have a list of stuff not to take - things I always found myself packing and didn't use.
We each check one rolling duffle, and have a typical rollaboard stye carry on, and a small backpack as a personal item. We don't have trouble keeping the checked bags under 50, and mine was closer to 40# last time. The rollaboards take some of the heavy stuff as long as it's not an airline where they care. (Where you are you'll likely need a different strategy.) My husband's backpack is one of those clown cars of a camera backpack that holds an amazing amount of his camera gear. He does have a generic hard rolling bag with foam he has checked if we'll be on an airline where he knows he probably won't get away with such a heavy personal item no matter the size.
