The PDM is much easier than the wire plus, but I don't even know if you can get them anymore. There are a few threads in here about it, do a search. I installed 2, one early version the guy lost his horn, the other works fine.
I'm not sure if you can get a wire plus right now either. A buddy had been trying to get one for 6 mo. There are plenty out there so it works, just a lot of work to install it. There are a ton of threads here. I've done a shitload of the WP units, it's not that it's hard, it's just a lot of cutting and splicing, the install is messy unless you spend a lot of effort cleaning it up, and if you do have a problem, it's tough to trouble shoot.
If it was me, I'd rewire the whole bike for a standard harness every time, but if you lack the experience I'd go PDM, unless you can't get one then your only choice is the WP.
Install time for a total noob on the PDM is going to be 2-4 hrs. Wire plus 8-12.
