I have to stand with Sawn on this one. When I'm with my caving buddies, I use the systems they use, which is the Texas, the Mitchell and the Frog. I wouldn't consider using ANY of these in a tree, unless it was strictly recreational and for the purpose of ascent to a determined point with the intent of just coming back down.
Using two individual ascenders I always found more complicated than using one set of dual ascenders, which can be used for Ddrt, DbRT or SRT on 13 mm or 11 mm. These are secured (backed up) simply and instantly. The duals are unclipped once aloft and you swap to a friction system of your choice. Switchover only takes a matter of seconds while you're ihn a comfortable spot and fliplined in. Simplicity is of essence as the work aloft can bcome technical and the last thing you need is to be wrestling with the gear that's supposed to be helping you.
The Texas is a fabulous system for pure vertical ascents, especially with noob climbers as it is functionally sound. It's just grossly overcomplicated, timely to set up, slow compared to other options and not ideal to work off of. It's a pit caving system, not a tree system except, like I say, major vertical recreational ascents. If I were taking a beginner up a giant redwood, I would set them up in a Texas system.
As far as a self-belay prussik on SRT, I would consider that only in an emergency when no mechanical option is available, but not as a working system. To descend you almost have to use a footlock to add friction, as well as both hands, one on the rope and one on the prussik. You should be able to work off a belay system using one hand, or no hands, and keep everything else freed up. A prussik simply does not allow this.
SRT really does not lend itself well to friction hitch systems. To control friction on SRT with absolute control and precision, I've tried traditional hitches, advanced hitches and mechanical devices of all sorts. The friction hitch on SRT has been one problem that I have just not been able to solve. Any number of devices work marvelously well, even the simplest like an ATC or other tube-type devices. Occasionally, I enjoy a simple, fat aluminum ring, the same as those that come on a friction saver false crotch.
There's a lot of beauty in simplicity. The mechanical side of treecare is not that scary
