I have both, the Poker II and the HHKB Pro 2 (black with white alphas and black mods). After I got the HHKB, I put the Poker II into its box and back on the shelf. Then I got a second HHKB for work.
Things I like and dislike about the two boards:
Poker II likes: 60% form factor, standard layout, Cherry-compatible keycaps, standard keycap sizes, programmable.
Poker II dislikes: Cannot remap Fn and Pn. Don't like the sound or feel of Cherry switches (tried black, blue, brown, and green) and Cherry stabilizers.
HHKB likes: 60% form factor, HHKB layout (the best there is, IMO), dye-sub PBT keycaps, Topre switches, overall design, styling, symmetry, and feel.
HHKB dislikes: might prefer 55g switches, might prefer Type-S switches (but expensive, and not available with black case), might prefer steel plate-mounted switches to case-mounted switches.
Although the list of dislikes for the HHKB seems long, it is really a list of possible preferences rather than actual dislikes. Overall, I much prefer the HHKB to the Poker II. The HHKB is just more appealing on every level, including appearance, sound, feel, and layout.