I will highly recommend the Holosun HS507K X2. Not sure on the XDM but you may have to alter the locking lugs machined on the slide or use an adapter plate. I chose to remove the rear lugs and shorten the front lugs on my Hellcat instead of using the adapter plate. This allows me to still use the factory iron sights should the RDS fail when I need it most. Using the adapter plate you will probably have to add suppressor height irons to still get a sight picture if you wish to be able to use your irons for backup. This Holosun is one tough RDS. Mine has been dropped more times than I’d like to admit. I’m a machinist and carry this daily in the shop and it gets bumped all the time. It’s a circle/dot combo and you can use either the 30 MOA circle or the 2 MOA dot or a combination of both. The controls are easily accessible, battery life is excellent and it has a battery tray so the RDS doesn’t have to be removed to change the battery. I also have a Sig Romeo that is ok, but its a composite body with a plastic lense, dot only, has to be removed to change the battery and the controls are hard to get to under the shroud. It is cheaper and no modifications had to be made to install it. I chose to switch to the Holosun because of its tougher construction, glass lense, ease of controls and battery changes.
One advice I will give is avoid the auto brightness models. If you are standing in a shaded area shooting into the sun it will more than likely be too bright or too dim.
Another one I’d look at is the Swamp Fox. I’ve heard good things about them, but have never had one in my hands so I can’t give any first hand experience.
Edited to add: This probably goes without saying but make sure the one you pick will fit the width of your slide