I like the 8 shot one for burst because you don't need to take full auto or tube mag in order to not waste shots on bursts. It also has decent damage - I would suggest forward grip for +10% precision on bursts. Note, that precision doesn't need to be terribly high on shotguns, especially when bursting, unless there is only a single enemy.
For the single shot shotties, I like the vindicator - bonus crit damage, highest damage range (which doesn't hurt so much because you'll be shooting 12 & 20p in the later game) with a forward grip. This lowers AP cost to 20 which fits much more nicely into standard AP values for most builds than 25 - it's part of why spear is for the most part superior to sledgehammers - free belt slot (doctor's belt anyone?).
I suggest though, that you make a save and then buy a couple of frames and mods once you get to mid levels and then see the differences between the shotguns yourself. There is a quite a range of difference between different shotgun types and mods, and you can then decide if you value range and precision on your shotgun or close range devastation. Have fun!
