As far as I know, yes, the old one is deprecated (it says so here http://developer.android.com/reference/gcm-packages.html), but still works.
I would recommend using the Play Services version, though, since it's MUCH easier to configure and use, and if you don't need G+ login or anything else you don't have to use it. Yes, your APK will be a little bit bigger, but I think it's worth it.
Plus, any new features or improvements to the protocol will most likely be only for the Play Services library, and not for the old one.