The pin jaws are primarily use in expansion mode. I thinks the mini jaw set would be more versatile.
One thing to watch for as you get into this hobby is buying things you think you might need before you actually need them. (Same goes for flatwork though, too.) I've got a bunch of tools that seemed like a great idea at the time, since it seemed everybody had one, only to find that I seldom if ever use them. I'm not saying the mini jaws or pin jaws fall into this category (and in fact you might use them a lot), but just wanted to pass along the caution. The abyss is expensive enough...no need to buy things you won't use.