"The position too near the wall, so to speak, usually manifests itself in nearfield reflections, a larger problem imho than port constriction." - Lrsky
Well said - I agree 100%.
Regarding port location, note that if the speakers are designed for placement near room boundaries, the location of the port relative to those boundaries has already been taken into account. Audio Note, for instance, designs their rear-ported speakers for corner placement. Best to examine the specifics of a given speaker design rather than make decisions based on "rules of thumb" that have notable exceptions.
Even if a rear-ported speaker wasn't designed for placement near the room boundaries, in many cases it's possible to lower the tuning frequency by lengthening the port and/or reducing its cross-sectional area. This causes the speaker's inherent bass output to start rolling off higher up but not as steeply, so that it synergizes better with the additional room gain. This can of course also be done with a front port also, but it's more likely to be visually unacceptable.
One acoustic argument in favor of a rear port is that in most cases, with a bit of toe-in, your two bass sources (woofer & port) are now a different distance from room boundaries in all three dimensions. Thus their outputs will interact with the room modes a bit differently, in some cases smoothing the in-room bass significantly as compared with an equivalent front-ported speaker.
Finally, nearly all ports have a resonance in the midrange region (imagine talking through a cardboard tube), so all else being equal we'd like that unwanted midrange energy to start out facing away from us and to travel as long as path as possible before reaching the ears.
Duke
dealer/manufacturer