I've played both.. I only got a few hours into Eternal Sonata tho.. Since you get $$ for takeing photos and takeing photo's is hella easy it sorta makes $$ in the game pointless and you can pretty much buy anything by jus grinding a few battles.. But the graphics were amazing, i didnt get too much into the story tho..
Tales Of Vesperia on the other hand is a really good game.. The story is a little bit cliche, princess in trouble and the world comeing to a end, and it's up to you to save it.. But the battle system (real time) is cool and the graphics are nice.. I really liked the game myself

definantly would recommend it to any RPG fan.
Still, Star Ocean 4 is probably the best JRPG out for the next gen.. I'd cop that game over both Tales and Eternal Sonata.