I have the Leupold RX1200i and the Leica 1600B. In my estimation, the Leica is better. I have ranged over 1300 yds. with it but you better have a good target to get anything over 1000.
I have thever Leica 1600 as well, but would be almost impossible to find for under $500. After I played with the Sig Kilo 2000, I honestly thought the Sig was a superior device. It ranges faster and farther. Same compact size as my Leica and the Sig offers an additional targeting mode to shoot through rain and fog. The Leica does not have that option and it drives me crazy. The Leica is completely useless in rain, snow, or fog.
I bought my brother in law a Leupold RX1200i for his birthday because I was really impressed with the performance for the price. It's not as good as my Leica, but Leupold has come a long way since their first try at RFs, and for half the price, it really is a lot of RF for the money. Though I wouldn't count on it for consistent 1000 yd rangefinding in normal daylight. Just doesn't have the power.
I also owned the Nikon Monarch 1200 for a handful of years prior to buying my Leica 1600. Nikon is a good RF for the money as well, but dark LCD readout is useless in really low light and back light for readout blinds the view. It's size is pretty bulky for a 1200 yd RF. In normal daylight 800-900 yards was the absolute best I could do on hillsides and that was in scan mode with only occasional readings making it back to me. Low light, I could pick up 1300 yards.
Don't waste your time even reviewing or trying the Vortex RF, it's a pile of junk. Slow, will never read 1K, optics are sub par, and people have a lot of electronic failures.
Even with adding my Leica 1600 to the OP's list, if I started all over and did not own a RF, I would undoubtedly choose the Sig Sauer Kilo 2000. It's is by far the best deal for the money and offers the best performance, even better than the Leica 1600 in my opinion.
The Sig Kilo 2000 also offers one of the best warranty as far as RFs go. No questions asked lifetime (no receipt or registration and fully transferable) on the the optics and 3 years on the electronics. Most everyone else only offers 1 year on the electronics of their RF's. The Vortex is the only RF with a better warranty as it is no questions asked lifetime on everything, but the Vortex quality and performance doesn't even compare to the Leica, Leupold, or Sig Sauer