I've got the 3530LS and RRS TA-3. I've handled both the Feisol 3342 and 3372 with universal leveling bases.
If possible you would want to look at the Gitzo 3530LS rather than the 3530S, I think the 3530S is a bit short, an 8" difference. Shooting full height standing, using the tripod as rear support, shooting with the tripod on an incline are all situations where you'll need extra height. I know it's hard to find a used Gitzo though, and I wouldn't spend the money on a new one - just get a RRS tripod instead.
As far as comparing Gitzo vs Feisol models, I think it's more fair to compare the Feisol 3372 vs the Gitzo 3530LS. The smaller Feisol 3342 is a lot lighter (2.4lb vs 4lb) and while a good tripod it's just not as substantial as the 3 series Gitzo. It's more comparable to a 2 series tripod from Gitzo or RRS.
The bigger 3372 Feisol is very nice, super sturdy and light weight, about 1/3lb lighter than the Gitzo. I think the tripod legs may be a bit more rigid too. Both the Feisol and Gitzo are really good tripods.
Biggest difference IMO is whether you want to use the RRS TA-U Universal leveling base or the RRS TA-3 Leveling base since the Feisol can't use the TA-3 leveling base, only the TA-U. Both are very solid and lock down tight. There's maybe a small advantage to the TA-3 since the center of gravity of the rifle and rotation axis sits lower into the tripod, helping keep everything a little more stable. The taller you go from the tripod center crown (mounts, center columns, ballheads, whatever) the less stable it will be as a rule of thumb.
The other big difference between the RRS Universal leveling base and the TA-3 is the user interface. The universal leveling base has two paddles that stick out at 90 degrees from the head and are somewhat inset into the side profile of the base. When you are on the rifle and you reach up to grab the leveling base, your hand has to locate the orientation of the paddles and then make adjustments to tension. The paddles might be turned sideways or straight in line with you, all depending on how you put the tripod on the ground. It's just a bit less user friendly than the TA-3 where you can reach under the tripod and grab the handle, turn to tighten or loosen, as well as use the handle as an aid in orienting the rifle (almost like a vertical grip on an AR when aiming). The couple friends that I've seen trying out the TA-3 and Universal side by side preferred the TA-3 interface.
All this is really splitting hairs though, and as soon as you owned one or the other you'd quickly be used to it and it wouldn't be any sort of issue. The Gitzo TA-3 combo is my preference (RRS tripod + TA-3 if you have the $$), but the Feisol 3372 TA-U combo is badass and the Feisol 3342 TA-U is a killer lightweight setup. Not a bad choice in the group.
