Join Date: Feb 2015
Location: Oklahoma, USA
Car: '15 Outback 2.5i Premium
Feedback Score: 0 reviews
OE is Group 25. Group 34 is about 1" longer in length, about the same width, but 1" less height, so it has about the same internal volume. Group 24 is about the same length and width as group 34, but the same height as group 25, so it has the greatest volume of the three, so potentially can have the greatest capacity, all else equal.
Apparently all three will fit into the battery tray of a Gen5 Outback. You may need a spacer under a group 34 battery to make it a little taller so everything fits just right. If you have no unusual requirements, just get a good quality group 25 battery.