Between the two, I prefer Nespresso. Neither one of them makes coffee as good as a proper espresso machine, but Nespresso comes closer. IMO, Keurig is purely for convenience, but the taste is blah, alas, tastes differ, so YMMV.
Also, how much are those Nespresso capsules? Something like $50 for a pack of 50? Good quality espresso ground coffee in a can is significantly cheaper. And even a decent espresso machine can be had for less than $100. Granted, there is an extra step having to clean out the grounds after every cup, so Keurig/Nespresso win on convenience for sure, but I personally don't mind the cleaning. It's quick enough, and the taste is better.