I started with a dropweight, have had a couple of cranks, and now use an electric (Wise Tension head). Here's my opinion:
a) If you're stringing only for yourself, a dropweight may be adequate. I say adequate because they do get the job done. But, I haven't seen ANY good floating clamps out there now. Even the good ones have a lot of drawback that must ultimately be made up for on the tie-off string. <36 rackets/year, I'd say go for a dropweight.
b) If you're going to string for others, I'd want fixed clamps and a very sturdy mounting system (actually, I'd want that for my own personal machine too). I'd say these 2 things are a MINIMUM. Swivel clamps are more versatile, but glide bar clamps are simpler and more durable. If I was stringing >36 and <500 rackets/year, I'd go with a crank, fixed clamps. Machines like the Alpha Revo, Apex or Prince Neos come to mind (even a used Ektelon H if it's in good condition--but parts are getting harder to get each year).
c) If you're stringing >500 rackets/year, you're probably taking it pretty seriously. Top end cranks will do fine, but you'll no doubt read about "constant pull" being the standard, and want to upgrade eventually. Plus, it is faster, even if someone (I can't remember who said it) can string faster on a crank. If you can string faster on a crank, you're either cranking so fast that the string hasn't had time to relax yet, you're not used to the electric machine, or it's some other factor than the tensioner itself, such as clamps or you're just really familiar with the crank machine. Plus, by the time you start stringing >500 rackets/year, you're probably already looking as to how to step up next. I went with a Wise Tension head so that I'd have a crank backup, just in case something went wrong and I had some rackets that had to be strung. If you have a backup stringer, you might want to go with a straight electric machine.
These are just my guidelines however. Others will have different opinions.
