Meh. I guess they could both end up being fine, but right now they make eachother redundant, neither projects to become a defensive stud. Burke has such a puzzling way to build his experiment.
Two players, one has been compared to Letang and the other a Niedemeyer-light (same style, not saying he will be anywhere near that good... but a very valuable skill-set)
It's easier to teach defense then offense, and both players are very fast/agile... Which makes it easier to make up for their current defensive deficiencies. Also offensive Dmen hold more value then defensive Dmen.
Rielly has a higher upside, but Gardiner is a safer bet (Even though I really like Rielly's chances). I'll go with Rielly, but am happy we don't have to choose.