A 1 ct moissanite ring will be at most ~$1k, a 1 ct diamond ring will be ~$4k+. Even if you get $5 for the first ring and $3k for the second on the used market (unlikely), you still come out ahead.
1ct for 1K and 4K? You are being ripped off my friend.
moissanite.com has 2+ cts for rings starting at 1K. Bluenile, USAA, and Exceldiamonds all have 1ct diamonds with h-j color range and SI1-2 clarity for 1.7K-2Kish range.
Moisannite is cheaper, but not that much cheaper. Still a flawless looking 2ct moissanite ring for 1kish range is nice bling to show off.
Still the problem is resale. A good price, such as one off those sites, for a decent ring is still going to command a good price years later. Also chances are the diamond is going to last many many years. Moisannite, not so much on the resale value being held. Not to mention that there is a chance of it having problems.
Personally speaking. Anything over 1ct is gaudy as hell. The size just looks TOO big. Not to mention it tends to catch on so many things as a ring. In a real gold setting, having your ring catch on something 1 too many times is a good way to stress the setting which might pop loose that stone you have in it. Heard the horror stories of it happening more than a few times.
Moisannite is nice and I almost went that route myself. Actually would have if my GF's family wasn't some traditional catholic hardcases from Spain. So I got a ring that looks like I spent $5k from a retail store but really only spent about $1600 or so. On top of that, if they do decide to check if it's real, it most certainly will pass the tests.
Again, my personal preference was to own an Apollo diamond. But it looks as if that is never meant to be.