It probably does boil down to comparing HR8799's to Fomalhaut's exoplanet.
Pros for Fomalhaut b
1) It is the first confirmed directly imaged exoplanet in visible light. [Is it the first direct imaged exoplanet if we go back, since it was imaged in 2004 and I assume even then it was in visible light, right?] This first is unique from the rest and its too late to crank-up the band, I think, for an IR imaged exoplanet.
2) Warmer fuzzies with name familiarity vs. a number designation (as
t@nn stated).
2b) "Fomalhaut" is kinda fun to say. [My 3 yr. old niece thought bread pudding made no sense as why make pudding from just bread. Then she said "bread pudding", smiled and said, "That's fun to say!".]
3) The host star is bright and easily visible to the naked eye with mag. of about 1. [HR8799 is not really visible to most naked eyes with its mag. of about 6.]
4) The actual image from Hubble is stunning. Though impressive, the HR8799 image looks like something out of CERN instead of from Keck, at least the few images I've seen.
I still pose the question, repharasing... "Should we wake-up the slumbering cheerleaders and get them to celebrate one of these discoveries, or must we wait till we discover a stargate or something?"