[ctesla]

yes, the 34 group battery costs the same, and will have a larger CA/CCA/reserve..
if it will fit; you're gold..
subaru probably installed the same battery tray in vehicles, to keep parts cost down; and
generic means, they are always available, and swappable..
the larger base of the tray is probably for the group 34; and will probably fit;
just make sure of the hood clearance.. a larger, more powerful battery will not do
anything to your vehicle and system; except power it more effectively..
i just haven't worked on a '16 leg; so i cannot tell you what betteries will fit...
.. i did own a '93 subie AWD for many years, and a group 24 (ford) battery squeezed
in to the cavity pretty nice; w/o even needing J-hooks and tie-down bracket..
but then i switched to a Braille Racing battery, that was the size of cigar box, and weighed only 14lbs., and still had over 1000 pulse cranking amps; BUT--
my 93 had WAY less in computized controlled electronics than yours; so stick to
what subaru recommends..