Brewmate is simple and it works. Beersmith is a lot more complicated and takes awhile to get around it but offers a lot more features than brewmate.
If your just doing standard BIAB, single stepped mash etc then Brewmate is ideal for you. But if you want the ability to add stepped mashes and use the timer features to tell you when your step is finished then go with beersmith.
I recently switched to beersmith after using brewmate for a few years. Heres what i like about it..
Beersmith
Pros: Equipment profiles, Add stepped mash with timers, Inventory control to deduct ingredients from your stock levels, You can use beersmith mobile to create recipes on your tablet etc when away from home.
water profiles, the print out of the recipes looks cool. Add on packs allow you to update your grain, hops, recipes etc
Cons: Steep learning curve, costs money.
Brewmate
Pros: Free, easy to use, basic features and good for single stepped mash.
Cons: none really, it isnt as fancy as beersmith but some prefer that.
BTW You can add more grain options to Brewmate. I actually had a fellow brewer send me the file that contained the list of grains from his brewmate folder as he had a lot of supplier specific grain types setup in his. I openend his and mine in notepad ++ so I could merge them together and added that to my brewmate folder. I think I posted a tutorial on here somewhere on how to do it.