I too, own several vises. Being a metalsmith / jeweler I could probably consolidate or in retrospect only have gone with my Lindsay Truecenter PalmControl. It is extremely versatile, and literally the benchmark in engraving tools. If you will be working on mostly wearable items / jewelry...
That's a very open ended question that greatly depends on what you already have and plan on doing. You'll need compressed air to power the tool so that is the first order to tend to. I believe Lindsay tools has a C02 cartridge adapter to use as an alternative to a traditional air compressor...
Each tungsten piston is machined to very tight tolerances specifically to each hand piece. You may want to check with Steve if you want to use a new piston that didn't get matched to your air graver.
JF.
LOL. I've perfected a whole regiment with my laser printer (brother) . I tape a piece of parchment paper to a regular sheet of paper to print on. Before I run the print I'll lightly scuff up the parchment paper with a green brilla pad to help the laser ink adhere to the parchment a bit...