Unless they implement anger powered jetpacks and a special Angry Marines chapter, I doubt I'll be a Spess Merehns player. I don't really give a crap about how many play SMs on tabletop, they are easiest to paint, are almost godlike and... sort of boring. Heck, if anything, more of them to kill. I heard Tau plasma weapons do fine against spess merehns armor.
Oh, but if I get to roll an Eversor assassin... or a Vindicare assassin, yeah, then I would reconsider between Tau Empire and Imperium of MAn.