There are two general types of torches that work with glass; surface mix and premix. The most versatile type is called surface mix. Surface mix torches keep the fuel gas, usually propane, separate from the oxygen (or air) until both gases have exited the torch. The two gases then mix just beyond the surface of the torch's face. The advantage of this is that the flame is very quiet, the shape and nature of the flame is more adjustable, and most importantly for soft glasses, the quality of the flame is better than the flame produced by a premix torch. Soft glass is just about any glass that is not borosilicate glass, which is often referred to as hard glass. An example of hard glass is Pyrex. Many colors of soft glass, mostly opaque colors, when worked in a premix flame, will reduce and become gray. A surface mix torch properly adjusted to a neutral flame will keep the soft glass colors true. If you plan on working only soft glass or both soft and hard glass you should consider a surface mix torch.
A premix torch mixes the fuel gas and oxygen within the torch. Because a premix torch has a lot less internal plumbing than a surface mix torch, it is less expensive to manufacture and therefore generally costs less. Premix torches work well with hard glass, but as stated, they don't do well with soft glass. Premix torches are slightly hotter and noisier.
When deciding which torch to purchase take into consideration your future needs. A larger torch can make a small flame easier than a small torch can make a large flame. To get a hotter flame by working closer to the torch will make the flame too intense and you will probably just burn and boil the glass. A larger flame will give you more heat to melt larger glass without making the flame too intense. Also, because a larger flame covers more area, you won't lose heat from one area of the glass while heating up another area. Some torches have a separate center fire that can be used without the larger outer fire. This gives the torch a wider range of flame sizes. All the torches listed below use oxygen and propane or natural gas, except the Hot Head torch which uses MAPP gas or equivalent. Never use acetylene.