mmmm winter... nothing like having this to yourself and your two friends
but for the original question, ive tried both split toe and non and both work well. i have a 5mm non split toe right now (forgot brand, ill check it tomorrow) and it works wonders in 38 degree water in february.
i prefer round toe in the deep of winter b/c i feel like it keeps me just a tad warmer (kinda like mittens vs. gloves) & warmth is my priority during that time...that said, i wear 5mils & just throw a pair of medium weight socks on underneath. kinda does the same thing as having 7mils, but saved me the $$. i didn't think it was worth it if i were only going to wear them a few months of the year. the 5mils, w/ or w/out socks, i'll wear until april or so.
i also, somewhat contradictory to my bootie rationale, prefer gloves over mits or claws. i like the dexterity that having all 5 fingers available gives me. it's prob. psychological, but gloves make me feel more comfortable. claws & mitts (esp. mitts) make me feel claustrophobic & restricted. no bueno.
as far as brand, the dryloc stuff excel's been putting out there is really great stuff. kind of a pain to get into/out of, but top-tier stuff. i prefer rip curl b/c it fits me best. you really just gotta go hit up your local shop & try the stuff on & see what works. good luck!
I'm a 5mm fan, too... both boots and gloves. I wear a pair of SmartWool socks under my 5 mil boots for warmth, comfort, and ease of getting the boots on and off.
I don't care about split or round toe, and I don't buy by brand. The boot that has the sturdiest construction wins... reinforced at the stress points. Pull on and off a boot, and see where the material is stressed. That's where you want that thicker rubber reinforcement. Boots don't get stressed once they're on your feet, only when you pull them on and off.
As for gloves, I like claws. Having the index and thumb free is good for getting the keys out, putting on your leash, etc., but it's all personal preference. Some people's hands get cold, some don't.
Do yourself a favor and buy wetsuit glue when you buy your boots and gloves. You'll need it eventually, hopefully later rather than sooner. Wetsuit glue for the neoprene seams and for patching, and Aquaseal for where the hard rubber attaches to the neoprene.
I got the rip curl F-bomb 7 mils last year and I wore a pair of those Polypropalean hot socks as well. My feet were to the point where they were almost sweating. They only started to leak towards the end of the winter.
Far a gloves I got these 5mil oneils lobster mits but they started to leak in between my index finger and the section that had my other three fingers in it. I repaired them to get me threw the rest of the winter
I am gonna get the hyperflex ones this winter and see how they are . Hope they are as good as there suits
Im a big fan of Hyperflex. i picked up a 543 hyperflex ampseries hooded suit last year with there 5mm round toe booties and 5 finger gloves also 5mm and was super warm and comfortable all winter. And i dont think i paid over $370 for the whole set up.