I can't say anything about Battlestar Galactica, but Babylon 5 is great.

they are all very different. The starfleet ideas are unique.

bsg has a fight for survival with little techno babble. The tech is closer to what we can do already.

b5 is also about different species and their politics, but with the humans more like the todays jerks we are.

so i would suggest to watch both. Starting with bsg to not compare b5 with startrek so much.