In a nutshell, probably one you know you or your pet will wear.
The magnotherapy products can only be effective when against skin and they won't be so effective sat in your bedside drawer or in a cupboard, so do consider a style you know you will be happy to wear for as long as possible as often as possible. Ideally, daily.
There are two different brands listed on this website and both the 'Bioflow' and 'Pulse Magnetic' products contain powerful magnets, so you can be assured that you won't end up with a product which will barely pick up a paperclip and the magnetic strength will last for many years.
Prices range from £20 for a magnetic power pad to £125 for a Bioflow gold pirouette. Some people choose to wear one for work and one for best? The choice is yours!