Jacob, that is a really tough question, because each unit has its fans. In other words, there's obviously no right answer. As for my own opinion, maybe the best way for me to tackle it fairly would be for me to list pros and cons for each as I see them. Maybe others will join in here and offer their opinions as well. Here goes my take:
i-opener PROs:
-- socketed CPU allowing for a limited (but relatively speedy) upgrade path
-- LOTS of support due to a very large number of users
-- excellent flat-panel screen; not quite TFT quality but almost seems that way, very crisp & bright
-- very cool form factor, flat-panel unit suspended on silver bracket, looks great on a desk
-- hacking it imparts a satisfying "sticking it to the man" feeling
i-opener CONs:
-- no easy way to use your own ISP without serious hacking
-- modifying the unit requires replacing or reflashing the BIOS
-- modifying the unit for Windows, BeOS, or full-fledged Linux requires a hard drive and special cable
-- no audio in or out jacks (that's another optional hack)
-- modifying the unit is not for the faint of heart
iopener one more rebuttal PRO:
-- BadFlash.com makes BIOS replacement easy for the new version 5 i-openers (although removing the epoxy goop on versions 3 and 4 i-openers is a bitch with some potential for frying your unit permanently)
Webplayer PROs:
-- using your own ISP is a simple but fun, and relatively fast, hack (unless you use AT&T Worldnet or AOL, in which case you are screwed)
-- a more advanced hack which involves installing a stripped-down Win98 Lite on the built-in Disk-on-Chip gives you a nifty Windows 98 machine with NO hard drive
-- can take a hard drive if you like
-- audio in and out jacks are more powerful than the i-opener
-- a beginner is likely to have an easier time hacking the Webplayer than he or she would with the i-opener, no matter which hack is chosen
Webplayer CONs:
-- fake silver metallic plastic cover looks cheap and a bit strange
-- the display is somewhat washed-out, not nearly as bright and crisp as the i-opener
I hope this helps!
Randy