I personally say get the frame that fits you best(likely the same in this case) and then get it with the best components you can. I'd think you'll be just as happy on aluminum as carbon. The carbon may weigh a tiny bit less, but also has a reputation for breakage and many companies still recommend that you replace a frame or at least have it inspected by a professional if you crash it. Maybe you're a lot better rider than me, but I've wiped out plenty of times on my MTB. If I had to have it inspected and/or replaced every time...