Calipers are better in that they depend less on the hydration levels and bodyweight fluctuations. They are also much cheaper, with $20 you can find a reliable product. Tanita scales and other bioelectric impedance devices are not bad, but you'll have to accept that results may fluctuate greatly from day to day (and even during the same day), so you'll have to average a week's results for a meaningful monitoring of your progress.
Since you are blind I assume that someone will read the scale or the calipers for you. In the case of calipers, you will have to learn how to use them, but if someone reads a few relevant sites and shows you how to do it, you'll be perfectly able of doing it correctly yourself since it's a matter of feel and not vision. Yes, initially a scale will be easier but I think that in the long run calipers will be equally easy and more reliable. Let me know if you need links to sites with instructions on how to measure your bodyfat level with calipers.
Calipers measure thickness of skinfolds, so you will also have to plug the numbers in an equation in order to get your actual bodyfat level. This becomes less important as you get the grip of it, since no equation is completely accurate and you will eventually find that just reading one or two skinfolds is a perfectly good indication of your progress. There are also some digital calipers (like FatTrack) which compute automatically your bodyfat level, but you can't rely on the built-in equations for accurate results anyway.
Consequently, I would advise for calipers if you want a cheaper and more accurate assessment of progress, without the need of continuously estimating your actual bodyfat. But if you would like to have daily a bodyfat estimation without having to use equations, then go for the scales.
