File: 1335533332.gif-(366 KB, 400x328, 130756670535.gif)
There's a bunch of reasons why I'm liking the AO choice to represent Mass Effect.
FIRST It's already roughly at that apparent tech level. Kinetic barriers exist in AO as a casting effect, for example, so make it tech-based and you've got your barriers. Omni-tools sort of exist in-setting, so a bit of tweaking and you're done. It's a system built to handle a huge variety of character power levels (stats go from 1-100), so it's relatively easy mechanically to drop ME into it.
SECOND AO doesn't have fluff that is inexorably tied to the crunch. Star Wars kind of does, for example; using SAGA to play ME still feels like you're playing Star Wars with different names. The way the Force works, for example doesn't map especially well to Biotics.
THIRD (This is probably the most important to me) The rules are specifically built to handle "smart", tactical firefights, and to resolve them in ways that feel "realistic". ME is a shooter at heart, and so using a ruleset designed around portraying that only seems right. D20 Modern, for example, doesn't model firefights especially well, given the smallish damages guns do, large HP pools, and so forth. In AO, if you go running at a couple of guys with guns while waving a sword around, and they have a bit of space and a clear LoS, you're going to get shot up something fierce practically every time. I've seen that exact thing NOT happen in Alternity, d20 Modern, SAGA, nWOD. Since that annoys me and basically my whole group (a bunch of vets), we like AO for modeling the result of that action correctly.
Finally, fuck the spam filter. I had to reformat this fucking post eight times before it figured out it wasn't spam.