Welcome to our forum. There can be many replies to your post as people with different set ups for different purposes share their views. Defining yours a little more for us may focus the answers you want.
The Search feature here is a little weak, but worth a try: Red Dot Sights.
Here is a post from a few years ago to get started:
RED DOT SIGHT CONSIDERATIONS
I have four pistols with RDS. One full size 9mm M&P (pictured) with the slide milled for the Trij RMR. One Shield 9mm M&P with a Shield (brand) RMS milled on the slide. A Glock 19 + a 17 each with an RMR milled.
All have co-witnessed iron sights. Mine are all set up for personal defense/every day carry.
Both sights you mention are great quality, with the RMR usually declared the King. The Delta Point is somewhat larger and I believe sits higher, making it harder to co-witness iron sights. The new Holosun 507c (compact) has the same footprint as the RMR, costs somewhat less and has impressed many reviewers.
I am not a fan of generic mounting systems like the CORE. They start off as compromises and don’t get any better. If you don’t know what sight you want, a CORE is an OK option to try different ones, but you can do that for free by finding other nearby shooters with RDS who will let you shoot their’s. If you know what sight you want, and you are on the right track, mill your slide for that sight.