An Extender is good to have, as are lots of Devices. 5 EFC digits are better than 3 (not an issue in the current crop of remotes). Phantom devices increase the device count as well. The other columns aren't important when choosing a remote. However, I have to admit I have no idea what the protocol column means.
All macros max out at 15 steps each on most JP1 remotes (make that 20 on the 10820). But with an extender, macros can call other macros, making the effective length unlimited. Since the macro and keymove memory is shared, it's hard to say what the max is. I can say that in the models you're considering, I've never run out of space. I typically have around 30 macros and probably as many keymoves.
Without an extender, you can generally program 2 macros per key per device to any key except the setup button. With an extender, you can generally program 4 per key (primary or short press, shifted, xshifted, long or double press). That's a theoretical max of 800 spots for macros on an average 5 device, 40 button remote. So you don't have to worry about running out of macro keys. You only have to worry about putting them in intuitive places so you can remember where they are.
In addition to more ways to call macros, extenders give you some additional features like device state tracking (TOAD-Togs), key group mapping, device multiplexing and more memory.
The RCA doesn't have an extender yet, but the 8820/10820 does. In spite of that, I like the looks and the layout of the RCA best, so that's one of my main JP1 remotes at the moment. Even without an extender, the RCA can do device specific macros, pauses, multi-macros, and fast macros, and is 8 device including phantoms. The RCA is also cheaper and easier to find at a local store.
Those are all nice features which aren't on the chart. Aside from the extender and devices columns, I don't think the chart is a good feature comparison tool. It's simply a list with a few important attributes of each model so someone can pick the right cable, etc.
I don't know what features an unextended 8820 has. One thing I don't like about either the RCA or the 8820 is the lack of backlighting. Some Atlas and Insignia remotes are backlit. Atlases are also quite cheap and have an extender. They're a little short on devices though and can't learn (generally).
Bottom line is, it's really complicated picking out a $15 remote
) so I'm left with those three I mentioned.