If your core is warm, the need for gloves is reduced as your body does not reduce the blood flow to the extremeties. So the good news is that a dry suit delays the onset of the need for gloves. Of course, once the water temp exceeds the ability of your undergarments to keep you warm, you are going to need gloves realy really bad.
There are three types I'd recommend every diver have if they do both warm and cold water.
1) protective gloves to protect your hands in wrecks, etc. (thin leather palm, stretchy back, very little if any thermal protection.)
2) 3mm gloves for warm to cool water when the need exists. They don't really have a serious impact on dexterity if they fit properly.
3) 5mm gloves for cold water.
If you dive really cold water and use a dry suit, 5mm gloves are usually enough even for ice diving, provided you insulate your core enough to keep it warm.
Dry gloves are another option for exteme cold water dives, or for extemelylong dives in cold water. But they are a catch 22. If too loose they are a PITA, and if too snug, they are cold as they lack the airspace needed to loft the glove liner insulation. You need a perfect fit between your hands, the liners and the gloves for them to work really well in cold water without losing dexterity. And. the glove rings area PITA and get in the way of stage bottles etc. Also, they are prone to being pounctured and flooded and when that happens the are just plain cold, so if working around wrecks, rusty cables, sharp objects, etc. wet gloves make a lot more sense.
If you practice diving in your 5mm gloves, diving any of the rest is really easy. For example, I practice laying line, placing jump lines, cookies etc at depth in 5mm gloves and 42 degree water. When you have that mastered, putting in a jump in 3mm gloves, thin protective gloves or with your bare hands is a snap.
How the gloves fit is important. They need to conform to your hand with no voids or loose areas in order to minimize water circulation, yet you do not want them to be too tight as that wil restrct circulation.
Gloves also get old and when that happens the seams begin to leak. Leaking seams equal cold gloves, so when you fel that happening demote them to warmer water use and get a new pair for cold water use.
I like henderson gold core gloves, and find they go on with less stain on you or the glove if you use just a bit of water based lube (KY, etc) in the glove to help it slide on. The gloves will go on quicker and last longer before the seams get stressed and leak.
