Generally, at least in my opinion (and in the experience of others), a sporran is vastly superior to an over the shoulder bag, or even a rather large clutch purse. I suppose it's a guy thing, like not wearing fishnets and stilettos with a utilikilt...

Seriously, if you've got more stuff than will fit in your sporran, you are probably carrying too much junk around with you. In mine I've got a coin purse, a slim wallet (cash and credit cards), car key and house key, and my cell phone (which has replaced the pistol I used to carry off-duty). And that's pretty much it. If I'm going to something dressy I ditch the cell phone and add a cigar cutter and lighter.

I can't imagine needing to carry around more than that, but if I did I'd probably strap on a fanny pack.