all things being equal, the second frame will feel slighly shorter, as the SA is less, so even though they have the same measured ETT length the second bike is being measured from slightly further back.
To sort this out you can either just move your saddle around, or just adapt your riding to it. However, if you fit a shorter stem as well then you'll make the cockpit shorter still, so just be aware of this.
The new frame is slightly slacker which (equals more stability) but the chainstays are shorter (which does the opposite) so they kinda cancel each other out. I'd suspect you'll just have to think about how you want the bike to handle and adjust accordingly... the new setup may well descend a bit better (more stable AND yet more responsive) but won't quite climb as well, or at least one where you end up on the nose of your saddle a bit more.
All these things are a compromise - you just need to decide what you want it to do well and gear the setup around that.
Do you have travel adjustable forks? That'll help.