My local paint shop seems to have different ones in stock every time I go in. I've not noticed a lot of difference between the brands. I'll use brushable seam sealer if I want to be quick (maybe doing an Aston Martin or something), or the PU stuff for a mastic gun if I'm being neat and tidy (Renaults).
I used to use 3m stuff on restorations, not the cheapest but its good quality, have a look here the brushable ones are good on floor pan repairs, and tapes, good for bolt on panels, also referred to as bolted panel sealers.
my local place sells TEX, worked fine so far and smells o so good just open a door when you start seeing purple dots.
i use the brushable stuff as the gun one is a ****** to squeeze out i find