TC Tri

The three main types of trainers are wind, magnetic, and fluid. 

Wind trainers are really inexpensive, very old school, and extremely (extremely!) noisy.  They work very well, but your friends, neighbors, folks in passing vehicles, will hate you for the racket they make.

Magnetic trainers are much quieter, but don’t typically provide a good ‘resistance curve’ — the degree of resistance needs to get harder more quickly as you go faster, just like it does in real life — compared to other trainers.  They’re reasonably affordable, and can be manually adjusted to change the resistance as you ride, often via a handlebar mounted shift lever.  The exception to these are electronically controlled models which measure your speed and match resistance accordingly.  A computer on the table or in the unit does the adjusting, and price goes up dramatically.

Fluid trainers are (imho) the best of both worlds.  Quiet, excellent resistance curve makes the experience very much like riding on a road.  The only downside to these is that the fluid units A) are heavier than others — not a big deal, as you presumably don’t take it in a suitcase with you and B) get pretty hot.  You’re not going to start a fire with one, but you can burn your fingers on them after just a 20-30 min ride.

For my money, Fluid is the way to go.  Reasonably priced, you don’t need to mess with it to get a road-like riding experience, it’s not deafeningly loud, and it’s very durable.  If you need to spend less, get a manually adjustable magnetic trainer, and resign yourself to adjusting the trainer’s shift lever when you also shift on the bike.  If you want to blow $1500, get a computrainer, and pretend you’re training in the Alps all winter long