If you dont already have skyrim, mass effect 3, or saints row the third payed off, you should skip both of these games for the moment.
Dont get me wrong, their both good, but i dont feel that their worth 60$. I like Dark Souls, but 70% of your deaths, you will only learn "Ledges Suck" or "Big guy kill me because i didnt stay on the path i didnt know was the correct one". Its a great game, and id be more then happy to buy it, but it suffers from lack of direction, in to big of a way. They went from "Not holding your hand" to "Hitting your hand with a hammer, and telling you to watch out for the hammer next time."
And Batman is an amazing game, but the controls are a tad bit clunky at times. Id say buy it if you can play a story game 4-5 times. I can really only go through story games 2-3 times before they start to bore me, but thats just me. But Batman: AC is a fun game that hits all the nails on the head, without breaking any of your fingers.
Id say, if you have the option, rent them both 2-3 times, or just wait till they drop in price a bit.