I just started reloading about a year ago.
I spent about a month doing research looking for what the best, easiest options were for my needs.
I wanted to reload mainly for cheaper range ammo, and maybe one SD load so the wife can shoot my 357 without hesitating, but still have enough power.
After a lot of searching for my personal use I decided on either Unique or Universal. I went with Unique of the two simply because its stocked here at Gander Mountain, and of the two Universal seems to be out of stock more often (I think its more popular here at least and is being bought out quicker).
I like the fact that Unique isnt so temperamental. And the bulkiness makes it easy to see if your double charged. So for a beginner like me it was a good powder to start with, plus its not a bad powder to just stay with. Lots of old timer loaders use it. It can be used for shotgun recipes too, so unless I get into loading rifles, I can use it solely indefinitely.
Thats how I narrowed it down, anyway