I put together a spreadsheet for ACR comparison, it is also an attached PDF. It makes it a little easier to compare the features side by side.
The obvious difference between 7620/7622 and 7610//7611 are the current ratings. It should also be noted that 7620/7622 are Magnetic Latch Relays, and thus have a lower operating current 13 mA (their change current is high, but only when changing states) The 7610/7611 operating current is 15 mA open, and 175 mA closed. The 175 mA closed is still pretty low.
The 7620/7622 also gives you a switch to close the relay (Start Assist) and open the relay. The switch also houses an led indicator, that can provide ACR state and diagnostics information. The 7610/7611 can be wired for an optional LED to perform switch state and diagnostic information. I recommend wiring in the optional LED if going with 7610/7611
The 7622 also has a manual switch on the top of the unit. This will allow you to open and close the ACR Manually if the smart battery monitoring logic were to fail, it also gives you the ability to lockout the ACR if you are performing maintenance on the vehicle or taking it into a shop. (they won't find out the hard way there is another 12 volt source) You could add a manual switch to the other units if you wanted to duplicate this feature.
This feature also comes in handy if you accidentally drain your house batteries to low, the 7620/7622 & 7610 have a low voltage lockout setting of
9.6 or 9.5 volts. While the 7611 does not have the low voltage lockout, at some conceivable voltage I expect the ACR would fail to operate.
The 7620/7622 & 7610 can all be wired to perform start isolation, they will open during while the key is in the start potion. The 7611 can not perform this feature.
The 7611 has an Auxiliary Priority (Optional) setting, that can change the open low voltage to 12.25 from 12.75.
-greg