If your main problem is Rats, buy the Long Flap Rat Trap. It will also catch mice.
If you have a mostly mouse problem with an occasional rat, buy the Long Flap Mouse Trap.
If you just have a mouse problem, buy the original mouse trap.
If you plan to move your trap around and some times near outlet and some times not, buy the AC/DC option.
If your trap will not be near an outlet, buy the Battery Powered option.
If you are a Do-It-Yourselfer and have a soldering iron, buy the self-assemble kit and save yourself some cash.
SIDE NOTE: We have been testing the battery life in a couple mouse traps starting 11-23-20. Triggered it every day for the first month now just triggering every couple days or once a week. The battery is still at 5.37 volts as of 5-27-21. The servo will continue to operate down to 4.6 volts. The 4 Duracell alkaline batteries voltage started at 6.42 volts. The traps have been indoors. Battery life will degrade much faster in colder temps. 6 months and still going strong.