If there are games you'd like to play on the 3DS then get lor. But region lock on the 3DS can be just as frustrating as the lack of Vita games unless what you want to play is surely available for your 3DS region of choice.

To keep or not to keep depends on your own budget, no harm keeping, but then no point keeping too.

Personally, if you already one, it's wiser to save up for the other. Both are very varied experiences. And offer a variety of items that you can play around with.

Just keep saving. Games will come, and who knows. By the time you have enough money for a 3DS, you might just get something else for the Vita.