First place I owned was in Ballston. Its a step down from Clarendon but its not bad at all. There is a Harris Teeter right on Glebe so shopping is close.
When I lived there Ballston Mall was starting to get shaky - they had not built Kettler yet. Plenty to do, but not the vibe of Clarendon.
Clarendon is definitely a place for the younger set and for the newly married who are child free!