Wow, this is a tough one!
What speaks to my heart the most? Hmmm.
I have a few, so I have to think about it.
I am REALLY enjoying the Caspian I just finished building and now am able to start shooting.
It would be hard to part this with that one I just shot the second 100 rounds through it and obtained a 7 yard group I've never come close to in a .45 before: 8 rounds touching in a hole about 1 1/4" wide outside edge to outside edge. Yippee!
But, I really like the feel of my 1993 Hi Power Mark III also, and I love the story that I had a forum member find out he had put a deposit down on it 1 hour before I got to that store, so he backed out and turned the gun over to me. What a guy!
It would be really hard to part with that Hi Power. Especially since 9mm is so much more affordable than .45acp.
However, I'd probably be like a couple of others on here and have to stick with my customized Argentine Sistema. Frame and MSH are original, but that's all.
After my last bout of working on it, I was able to put 50 rounds into this sized hole at 7 yards with the Sistema.
My hands/arms have a bit of a shake to them, and my astigmatism makes longer range shots harder, so I consider this a good starting point for my accuracy work: self-defense range.
I will be working to get myself up to the 25 and 50 yard range shots someday, but not yet.
It would be really hard to choose between the Sistema and the Hi Power [which has a similar sized 50 round group at 7 yards], but I'd probably lean toward the Sistema, as I did more work to it so it feels more like 'mine'.
But, that Caspian may surpass all of them within the next year: it feels SOO nice!