I just did a manual workup of all 3-homer games since 1992, split out by team’s home stadium. Note that this doesn’t take into account stadium changes–for example the numbers for Washington include all 3-HR games by Expos or Nats hit at home, and all 3-HR games by visitors at the Expos’ or Nats’ home stadium.

Team   H    V   Total
CHC    9    8   17
COL    8    9   17
TEX    9    7   16
CIN    9    6   15
BOS    6    5   11
TOR    6    5   11
MIL    7    3   10
PHI    2    8   10
CLE    5    3    8
ARI    4    3    7
BAL    3    3    6
DET    3    3    6
KCR    0    6    6
NYY    5    1    6
WSN    2    4    6
ATL    1    4    5
CHW    1    4    5
HOU    2    3    5
LAD    3    2    5
SEA    2    3    5
STL    3    2    5
OAK    3    1    4
SDP    1    3    4
LAA    2    2    4
PIT    1    2    3
SFG    1    2    3
TBR    2    1    3
FLA    1    1    2
MIN    0    2    2
NYM    0    0    0

So these are 3-HR games by home-team players, and by visiting players, and the total.

Check out the disparities for the Brewers, who have hit a lot more at home than their visitors have, and the Phillies, who have yielded a lot more at home than they’ve hit.