The various decoder manufacturers may have a specific recommendation at their respective websites - try looking up Lenz, MRC, Digitrax. Soundtraxx, TCS, etc. Kato may also make a recommendation as manufacturer of the loco in question.
However, it probably boils down to the fact that there is no single "right" answer. Many of the decoders from the companies above will work; it depends on how much you want to spend, and what features you want/need in a decoder.
Andrew