I have the ratchet, it's not really powerful in the sense that it's gonna break fasteners loose, but it has a regular ratchet head so u can do it by hand and then spin the bolt or nut off with the motor.. for me, it's really just a toy - but alot of mechanics give it great reviews. All cordless ratchets are like that - unless u get a pneumatic reactionless or impacting version.
As far as the impact, The 18v is gonna be more powerful. I have the 3/8 fuel and 1/2 fuel both in the m18 platform. When I can use them on occasion, they make things easier.. it will all depend on what you're gonna do with em.. some mechanics really like the 12v, others prefer the m18.. everyone is doing different things with them, so really you will be the best judge of what will be better.
If you're the kinda guy that wants to do his own brakes, and bearings, and stuff like that the m18 might be worth it.. if your typical projects are more like lawnmower and home repair stuff the 12v is probably a better buy since you already have batteries.
I just used the brushed m18 sawzall to cut a solid 1" thick utility pole anchor below the ground line that we abandoned. Made the cut in seconds.. a 12v could probably do it , but Id be asking an awful lot out of the tool every time I had to do it.
