Thanks. I never like being completely without melee capability since I know I'm going to be subject to it eventually (he says while assembling a Tau kill team).
I agree that the double shuricat Exarch is most efficient - unless the melee options were substantially better he'd have to be, since he doesn't pay anything for having two shuricats and the diresword costs 2. But points efficiency isn't my only consideration: an Avenger Exarch who's engaged isn't using his weapons. One at long range is less likely to hit, and at short range anything can charge him (thanks to the +3" free charge distance everyone gets in Kill-Team).
The damage output per hit is about equal (1/6 less chance to wound for the diresword vs. T4 or less, but usually 1/6-1/3 greater chance to get through armour, disregarding 6s to wound - which are better for the diresword than the shuricat but in practice usually have the same result against 1 wound models unless the opponent has invulnerable saves) and that the number of attacks is close to equivalent (1 pistol shot + 2 attacks, essentially always on 3s, vs. 4 shots usually on 3s but sometimes on 4s). Given that, I prefer to use the more versatile option if I can spare the extra points (conveniently, losing Rangers can help there). I think the two are close enough that it comes down to preference - but this is entirely in respect of diresword vs. twin shuricat. I don't see any reason ever to take the power glaive.
EDIT: Something I neglected that complicates all this is that, of course, the Exarch gets two S3 attacks in melee whatever he's armed with, so the diresword then only really adds the save modifier where the extra shuricat adds full extra shots. That does make it look less attractive - and while much of the above applies in that you still can't use the guns when in combat, you aren't actually paying for them.
Thanks for the insight on Rangers. It seems strange that neither Rangers in general nor Sniper specialists in particular ignore the -1 to hit, but one of my Rangers is a comms specialist and so effectively ignores the long-range penalty.
Would you say the issue with the platform is with platforms generally, or with the EML specifically? As in, would a starcannon, shuricannon or scatter laser (why would you ever use a bright lance in Kill Team?) platform be a reasonable option? It's got me reconsidering my DS8 turret in the Tau list - though that has the huge advantage that it doesn't have any base cost so you just pay for the weapon, which is cheaper than any other Tau model. My instinct is that the SMS is the way to go because ignoring LOS seems very good in Kill Team, but the firepower output is only about the same as a drone (though at longer range).