I think probably Ellis, just for having produced the more consistent offensive numbers over the years. Trouba hasn't really had that. But i think in terms of peak play...Trouba has maybe been the better player, and he's got the bigger "big year" peak.
If i were picking a player to have had on my team through their career, i'd go with Trouba pretty comfortably. But in terms of broader fan perceptions, he's definitely had the "lower lows" in his career. And doesn't have Ellis claim to fame of being a cog in that "league's best defence" with the Preds foursome for a bit.