Currently I train on a Schwinn Airdyne. It works OK, but I'm looking for a trainer that will better simulate road conditions (gear changes rather than just pedaling faster) as well as give me saddle time on my own bikes. I'm looking for opinions on roller systems and fluid/mag trainers. There are a lot of brands out there too, so if you can speak to the advantages of one vs the other, that would be great. I'm looking to stay under $250 and have no issues with buying used. Thanks.