Seriously though, you will get some passionate replys to this post. I prefer the ms20 over the RS PIR. Those are the only two I have had sucess with but there are others. The ms20 for me is less sensitive to installation and location of the fresnal lens. Might be me but I can always get 40 to 70 feet out of the MS20 and sometimes only 15 feet out of the RS. Now if you keep tweeking the location of the lens, it will eventualy come in to 30 or 40 feet. (I mount them flat) I like the fresnal lens design better. I like the critters you get with the sections that look down. With Jons mods the battery lasts just as long. I like having the ability to sence at 50 to 60 feet (not all pictures are at night). They are cheap and readily avail at Walmart. I have a simple and easy installation method I use>
Okay, now can we hear from the RS Side.
Do A search, this has been discussed to great detail.
When you say "with Jon's modifications" do you mean the standard information found on Jessie's hunting pages for the MS20... the instructions on how to modify it? Or are there some other instructions somewhere that I don't know about?
Just a personal openion, but to me, the MS20 is easier to mount than the RS. The size is perfect for mounting in the shallow receptical box AEH found, which is a cench to mount. In addition, there is enough room left in the receptical box for just about any timer. As to difficulty, the RS may be a little faster to modify, but I've never found the MS20 to be difficult as long as you got a bulb solder sucker. To me, the speed of modification is about the only plus for the RS.