Hi! welcome to DRC.
As far as portables go, there are two to consider as far as the latest and greatest go for either Sirius or XM models go.
If you are using these outside in the wilderness, that already answers one question. Sirius's Stiletto 2 has built in Wifi for listening to stations via an internet connection eithout worrying about satellite signal. But, if this is primiarlily used outside, this isn't an issue. But if you like the idea of using it elsewhere and at home wirelessly, this is something to remember.
Also, The stiletto can record a channels for later listening, which is something you might consider doing when you are at home, then take several hours of content with you when you go out, so in case you have trouble getting signal while biking, you don't have to worry about skips in audio.
Thats where the XM unit, the XMP3 comes in. It features the same basic stuff as the stiletto 2, only it can record 5 channels at once. Also, both units feature removable mini sd card slots for your own content. I don't know which one would get better signal for you, and how well riding bike under trees and such would allow for crystal clear live reception, but with an external pair of antennea headphones plugged in, you may be in the clear. Someone with more outside expierence with either of these units can chip in. But thats as much as I know about either of the two radios.
There is always an option to get an older portable from either side, but I think the features in these newer ones justify dropping a few bucks to get them rather than be stuck with older tech.