I use all that you listed... each has benefits. The garnets are "sharp" and in the finer grits cut quicker than the oxides. The oxides are a good all around choice, but I don't pay extra for the cloth backed because I use fresh swatches for each pen. I've found the need to be careful with silicon carbides in the finer grits, especially on open-pore woods. The carbides detach or break off as the sheet wears, which is normal for all abrasives, but the carbides are very sharp and hard - finding their way into the wood grain. They have a shiny quality to them, so they stand out like a sore thumb. And since they are so hard they easily wedge themselves into the pores. I've found most of the oxides will not wedge themselves into open pored wood and can be easily removed with a puff of compressed air or a wet/dry vacuum prior to finishing. Just my thoughts, others may have found different results. I like the Klingspor brands, and do use MicroMesh since I occasionally sand through 4000 mesh. The MicroMesh is very expensive.
I found the multi-sided abrasive nail buffs (like Revlon, etc, found in the aisle with finger-nail files)a great value and they work really well to finish pens. They sell for less than 5 bucks, and are foam-backed so they take forms other than straight (tapered, curves, etc). The only thing I would caution about the nail buffs is since they are four-sided, if you use heavy pressure you can deflect the buff to the point the adjacent face touches the surface. This is a bummer if you have already worked through that grit!! I really like that there are 8 grits on these little buffs, two per side.
Bang for the buck? Aluminum oxide is an economical choice because so much of it is produced and sold.
