Re: how much better is this?
the thing about the shim method that makes it work is the tiny amount you have to add to make a difference.
if your chain seems like you need to remove an inch of slack, an 1/8" shim will do the trick. (that's not an exact measurement, just saying that a little does a lot.)
by the way, i'm talikng about flat shims that go between the motor mount and the motor, not anything between the seat tube and the mount.
as far as it misaligning the front mount;
on a diamond frame where the motor requires no custom mounts and fits perfect, all the shim does is raise the engine slightly. by adding the shim, this would make the front mounted higher up on the downtube, but it's still at the same angle to the frame, so both mounts will seat into the tubes properly.
on a cruiser, 99% of them need a custom front mount anyway, so unless you've welded your own onto the frame and they have no adjustment, some minor modifications might have to be done, but as i said, a small shim will do a lot, so moving the front mount up or changing the angle very slightly can still allow it to seat properly.
if for some reason the shims don't work, the other option is changing the sprockets, as i mentioned. on a coasterbrake, switching up (or down) one tooth (from odd to even or even to odd) will usually take out just the right amount of slack.
if you go from an even numbered tooth to another even tooth, you'll end up adding links into both chains, and still have the exact same problem.
now, all of this is based on someone actually having a chain breaker in the first place. i think there's a lot of people using the tensioner because they don't have a chain tool, or don't know they exist so they just put the chain on, add the masterlink, then mount the tensioner to take up the slack.
i worked on a kid's bike who had never even seen a chain breaker. after taking out some links, his chains fit perfect with no messing around with shims or sprockets.
i also have never used a half-link. if i did, i'd put it on the pedal side. but the whole concept of a half link baffles me. i know it works, i've seen it work, but it's a concept that sends my brain reeling when i think about it.