Lightning ball is great due to multiple potential hits, which, if those hits crits do a lot of damage
Nether Tentacle passes through mobs also,hitting once, but when that crits it's very large (requiring 2x LB Crits to pass it). I don't care about the heal here on that, just the damage.
So from a spammable ability standpoint with mob pass through, for me at least, it "appears" Nether seems to be better in a kiting aspect due to the potential larger crits over a bunch of smaller ones. (Which at 5% Crit It feels like I crit quite a bit on that ability for some reason. No idea why)