I have both guns. I like them both a lot. My full size has the Romeo1 and it's a great range gun. Love the optics.. just love it. The compact I carry. It's a great shooter just like the full size. Both are chambered in 9mm. Both are very comfortable to shoot. Both are quite accurate. I'm very happy that I have both. The full size is a bit large for a carry weapon and I wasn't that thrilled about the Romeo1 being exposed to the every day wear and tear. It comes with a cover but it would likely fall off and I would hate to have to remove it in a protection scenario. It's a range tool. It improves my shooting. And, it's just a lot of fun to use... a LOT of fun. I bought the compact 320 without the optics for the reasons mentioned. I love the 320 feel and enjoyed the striker fired system. I'm very excited about the modularity too. The smaller size, no optics to protect and worry about, and two guns that I can mix and match made buying the compact a perfect acquisition. I paid 665 for my full size RX and 530 for the compact. I will not part with either. Both have become favorites to shoot. If I could only have one... I'd buy the compact with the Romeo1. I would also get an non milled slide for my carry preferences. Many carry with the optics but it's just not me.
You will enjoy either. The 320 is a great Sig. Good luck in making a decision. Hard choice... Welcome to SigTalk and greetings from the flat lands of Kansas.