Honestly, I'd probably go for the alpha over the optimum. I wanted to like the optimum, but its damage codes are among the weaker of the ARs and shotguns. I mean, having an AR and shotgun in one handy package seems nice, but the Optimum's shotgun just doesn't have the oomph of normal shotguns. If you're wanting different tools for different situations, you already have a shotgun, but no grenade launcher, which you'd get with the Alpha.
And as people said, it depends on the kind of game your GM is running. If popping off a couple grenades is likely to get the hammer dropped on you by Lonestar, KE, or corporate security, and/or it would be too heavy handed a solution in most situations your GM would throw at you anyways, then maybe the Alpha isn't right either. When I was picking my weapons, if I thought it was going to be in a situation where I needed a shotgun, I wanted a real shotgun. And it would be rare I'd get to use the GL of the Alpha, so I actually went with the EBR. I can't do suppressive fire with it, but for all other situations where I'd need an AR type weapon, it works, it hits as hard as a shotgun and it doubles as a sniper rifle. It fulfills a lot of roles- and if you're getting a valiant, you have a suppressive fire role filled already anyways.