Thanks for your reply. The fact that a speed tie is so likely is actually one of the reasons that I was thinking of Eelektross over Thundurus for my 6th; if my Thundurus loses the speed tie and gets damaged by an Electric Gem Thunderbolt, he takes a serious dent, but Eelektross is bulkier. For this reason, Eelektross would also be nicer against Trick Room; the rest of my team is Mienshao/Tornadus/Hydreigon/Conkeldurr/Chandelure, and although Chandy has Imprison, sometimes I can't stop them from killing Chandy and getting TR off. With Thundurus, 5 of my 6 Pokémon would be fast and frail (Conkeldurr being the exception, obviously), which means I am pretty much screwed if TR gets up.