DS9 and TNG are both great but for different reasons.
TNG really stuck to the exploration aspect and had much more standalone episodes that you can just turn on, watch, and say "hey, that was cool."
On DS9, you watch the characters develop over the course of one long story arc (the dominion war). I hate comparing it to a soap opera as it might give a negative connotation but that's basically what it was.
If you don't have time to invest into an entire series run, go with TNG episodes.
If you have a good amount of time and can watch DS9 from premiere to finale, i think you will enjoy it. (During the original broadcast run, i couldn't get into it because i couldn't watch the episodes consistently from week to week. Once i got a hold of the entire series on discs, i watched all of them over the course of a summer and ended up really liking it.)