I guess it depends on your preferences. I once read into the first pages of Mac Lane and t.b.h. I didn't like it at all - the definitions and theorems aren't numbered, which I consider a sin for any math book. They don't even really stand out typographically, except for being written in italics. And there's way too much babbling around for my taste. Don't get me wrong - not saying anything about Mac Lane's mathematical knowledge... but to me, it doesn't seem like a good book.
If you're more into the "Bourbakian" approach, go for "Handbook of Categorical Algebra" by Borceux. I only had a glimpse of it so far and it seemed much better structured and orderly. Really looking forward to reading it myself, some day.
edit: Seeing that you only want to learn 'enough' for your research, I should probably warn you in advance: Borceux wrote three volumes. Not sure, how much of that you'd need to read to give you the knowledge you want. Personally, I still wouldn't read anything else, unless in the same style and with a more narrow choice of contents - if that's possible, keeping the depth.