I personally would go with "B". You can purchase rollers that also come with a resistance unit. You can even order a front stabilizer if you don't want your front wheel rolling as well. Working out on rollers I feel would better translate to the road as factors such as balance play a larger role as opposed to clamping down your rear wheel. Not to mention, if you wanted to get out of the saddle to simulate climbing, etc., you may put undue stress on your wheel/hub. Here is a like model you may be interested in: http://www.performancebike.com/shop/cboProfile.html?SKU=4250
I am currently using the model displayed in picture A. It's great for doing intervals, intense efforts because you don't really have to worry much about balance. I also bought it for around $70 USD, very cheap eh? Rollers, I'd like to have, but I would rather take the Magtrainer. Rollers are a) expensive, b) don't offer much resistance, c) needs an expensive resistance unit if you want more resistance. My primary reason for getting an indoor trainer was so I could avoid traffic, and unecessary stops especially during intense efforts. If the trainer cannot provide enough resistance to make me feel that I am working, then I might as well just go for an easy ride outside.
However, if money isn't tight for you and you can afford the rollers with the resistance unit, I bet you can get the Magtrainer too. Getting both types is actually the best choice...IMO.
I also like the Magtrainer's secondary purpose being a bike stand. Makes cleaning my chain easier.
Oh, speaking of frame flex, I see a lot of flexing in my bottom bracket. It sways a bit from side to side while I am pedalling. From what I've read, it is recommended that you do not to standing sprints when on an indoor trainer that is attached to the rear dropouts. The frame flex is especially bad when you are using an indoor trainer that is attached to the fork of the bike....avoid at all costs!
On the rollers, however, I believe there is no unusual frame flex.
One last thing, trainers really eat up my tires! My Panarace all-weather tires have become slicks after a year of using on the trainer. Not bad actually, considerign some high end racing tires last only a few weeks on the trainer. So use cheap tires!
as with nearly all my purchases, I did a fair amount of research before buying a "style A" trainer.
I bought a Kurt Kinetic (www.kurtkinetic.com) and believe it has to be the best. its a fluid trainer, but the fluid unit is sealed so it won't leak...its driven by magnets. it has a realistic road feel...20mph on it feels like 20mph on the road.
it ain't cheap...$300 US. i opted for the extra heavy flywheel for an additional $35 to make it a real "road machine."
i've riden it through 2 winters, about 10 - 15 hours per week, and have been thrilled with it. its my new best friend when its below freezing or wet and cold outside.
do a web search...there should be some reviews. Bicycling Magazine named it an "editor's choice" in the May issue.
it will, however, burn up a good tire...you can identify a trainer tire by the flat part in the middle of circumference. I have a spare rear wheel I use on the trainer, and run the tires I no longer feel good about using on the road (and wear them down to bare thread.)
yes, i experience flex, but I'm not sure I'd call it bottom bracket flex.
essentailly, you're alternately pushing down on either side of an object that is fixed at both ends. I look down and see the bike sway to either side of the centerline, but it is pretty much the whole bike swaying.
is this doing any damage to the bike? I don't know, but others with much more knowledge than me use them and say that's normal. don't know if its desirable, just normal.
I've never ridden rollers, but I like being fixed so I can watch TV or read w/o worrying about falling over.
I've got some rollers which i find excellent for speed work. I can also ride without hands and watch tv. For resistance I put it into the big blade and use the 13 or 12 trying and keep the cadence up high. often have over 75km/h on the computer.
Frame flex is normal and occurs on the road, on rollers, on mag trainers etc. I'm not sure whether the mag trainers will damage the frame but I'm quite happy with the rollers.
I've tried a mag trainer and just didn't like the feel of it. Be sure not to use kevlar tyres on one though as they chew up rapidly.