I'm gonna stop you right there, you just said an AR-15 is a high-powered rifle. It is obvious you don't know anything about guns and I shall ignore anything you say from this point on.
I have both Sigs and Glocks I prefer Sigs in a major way. The only plus I have for my glock is I don't care about jamming it between the seats or tossing it in a glove box. Sig Sauers are a work of art. I consider Sigs my sports car where the glock is my beater work truck.
I think I get my Sig obsession because after my dads department switched from S&W revolvers they went to Sigs. Everyone I have ever shot is a great gun. Price is up there but I think they are worth it and most of them will hold value if you take care of them. That being said I have both Glocks and Sigs and they both have their purposes.