An SSD has some advantages over back-up media such as USB memory sticks or external hard drives. It works very quickly, doesn’t require a separate external power supply, is much more resilient to knocks and falls than an external drive, and copes particularly well with the regular rewriting and file changes involved in back-ups.
The costs of SSDs, however, mean that it’s only really advantageous for particular types of back-up. There’s no real economic option for using SSDs for image-based backups where you literally make a back-up of your entire hard drive. And for back-ups which simply cover key documents, it’s unlikely you’ll find an SSD which can compete on price for USB memory sticks which are now available with capacities as high as 16GB.
However, if you wish to make back-ups which include a large number of audio or video files, and this takes you into the 32GB to 200GB range, you may find an SSD is a viable option.
The most important point here is that an SSD is currently only worth considering for back-ups if its features and benefits are suited to your needs. It may be several years before an SSD is competitive with other back-up options on price alone.