Well, my first question is what are they asking for each of those? if its a fair price (in other words, do your research online... some B&M notoriously crank prices up beyond a simple "markup")...
The Lavatube has been around the longest of those three,(and I've heard about the error issues as well with them) if I'm not mistaken, then the SVD, then the Tesla... I only know a little bit about the SVD myself personally... If you're looking for a mod that will perform comparably to the MVP, then I'd say any of the bunch are fine (though I personally am not a fan of the Tesla's design). If you're looking for a "big increase" in performance, I don't think any of those will really offer all that much.
For a little bit more than what I am assuming you're spending at the B&M, you can get an E-VIC... which has a ton of bells and whistles, and by all accounts may perform much better than an MVP... I dunno...Its really what you're after in your vape.
Same goes for the clearo vs. carto question... it depends on the device. I'm a big fan of EVOD clearos, but not so much of the protanks....Iclears are good, but I didn't like the vivi novas...others swear by the devices that I didn't care for.
Cartos, I prefer Boge, others prefer the smoktech. IF, and I do mean IF you can get them, Ikenvape cartos ARE awesome though.
Hopefully there was some help in there, but sadly, each vaper is different and will like different things.