Thanks, I'm sure they're all fine lights. One problem I have with all those lights is the fragile plastic mounts, (that also require a screwdriver)... My mtb nightriding usually involves a bit of crashing, so the less brittle the light mount the better.
The Planet bike mounts are fairly robust, and inexpensive (available separately). The light snaps in so you leave the mount in place. No tools needed. More than one bike? Buy another mount. Mounted under a seat on a set post, is a fairly safe place, not unassailable, but pretty good. They are light you could premount a spare. Hardware could be changed out for a wing bolt that could be hand tightened without a lot of ingenuity.
The HotShots Mount shaved off too much weight. I was thinking of adapting an old PB Superflash's clip to the HotShot. It did not make it home though I was sure it got into the car. So I did no do that. ;( Great light. Mount stinks.
The Red Zone 4's mount is a steel clip that you cinch to the seat post with buckle style velcro strap and a rubber pad. Since it is a wide angle light it is fine at the set post angle making it low profile. Because it is a stainless steel clip, a metal bracket could be made for it to clip to, (so could the other lights but their clips are plastic). It's $100 price is daunting, but it is almost as bright as a Turbo from straight back and many many times brighter to the side, more the wider the angle. Truck drivers and low sports cars will all see this light. Cross street drivers will see this light sooner than your reflectors will light up. Run time of about 8 hours on top power flash mode but four other flash settings with longer run times and three steady with the highest having a 6 hour run time. The internal battery is an issue as they have a 2-3 year life. Forcing a trade-in or factory rebuild, or 'just' a new light. It is waterproof to a fair depth, though.
If you need the lights to also whistle dixie and make you ride much faster, sorry.