Undergarment Comparison: White's Thermal Fusion vs Bare SB System Mid Layer?

[mahjong]

Has anyone by chance tried both of these? Is one much warmer than the other?

[driebel]

I'd like to add on to this question, if I may.

I'm new to drysuit diving, and my first guess on insulation was woefully inadequate for the 5C (40F) water I've found. I'm currently diving a DUI CLX450 suit with a set of merino thermals and the 4th element Xerotherms underneath. I've also added an off the rack sweatsuit, but am still cold (like bad shivering) after ~40min.

What are people's favorite undergarments? Reading the forums, I like the sound of the 4th element Arctic, the White's Thermal fusion, or the 4th element Halo3d. Obviously, these are different price points, but what do people think is the warmest/best of these three? Or is there something even better I haven't seen mentioned? Thoughts? Oh wise scubaboard, tell me what to do! As a calibration point, my preferred wetsuit is an 8/7 Henderson, which keeps me happy at 12C (50F) for almost an hour.

[TSandM]

I've dived the Arctic, the Whites MK3, the Halo, and the Thermal Fusion. The latter three are, for my money, MUCH warmer than the Arctics. The MK3 and Halo are very comparable in insulation. The MK3 is bulkier, but it also has hand-warming pockets, a nice breast pocket for car keys, and a butt zipper for non p-valve folks, which is very nice when diving in cold weather, where you don't want to shed the whole undergarment to use the restroom. The Halo is less bulky and very comfortable, but the only pocket is out on the right arm, which makes getting to your keys when you unzip the suit a bit more difficult. The Halo HAS to be dried in the dryer if it gets wet; the foam takes forever to air-dry.

The TF is considerably less bulky than any of the above. Like the Fusion, it takes a bit of finesse to get into the garment. (Might be easier if you didn't have hips.) It has hand-warmer pockets but needs a zipped pocket for keys. It does not have the butt zipper. It is VERY warm -- at least as warm as the two above, and maybe a bit better. It seems to take a bit less weight than the other two, although I did not do a formal weight check when I was diving it. It retains insulation when wet.

If your dry suit is easy to get in and out of and you have plenty of room for insulation in it, I'd say the MK3 is a great choice. If you're short on space, the Halo is an easy UG to get in and out of. If you tend to have leaks in your suits, the Halo is NOT a good choice, because of the poor drying. If you want to minimize bulk and maximize flexibility, the TF is amazing.

[driebel]

TSandM, that's EXACTLY the kind of summary/comparison I'm looking for! Thanks!