Magpul Pmags, hands down. They are the absolute smoothest loading and feeding mags.
I have various milspec aluminum, C-Products stainless steel, PMags. For aluminum I really like the Brownell's with PMag follower. They are consistently top quality and I would choose them second to PMags. I have retrofitted all my D&H and NHMTG aluminum mags with Magpul followers.
I have several 20-rd PMags in different colors I use for loading up different handloads when testing them at the range (black, OD, flat dark earth, foliage green). 20-rd mags are also lower profile for shooting from a bench rest.
For the 30-rd version I like the ones with a round count window. You don't see the rounds themselves until you get over 20 rounds, but a orange mark on the spring shows you the relative compression implying how full the mag is loaded.
If I was starting out I would get at least a couple of the 20-rd PMags, a couple Brownell's, and however many 30-rd PMags.
Lots of places carry these nowadays, but in the dark days of the last shortages
www.44mag.com had one of the best inventories and lowest prices for both PMags, milspec aluminum and Magpul followers and springs.