I measured the Inniskeen pitch on Google maps. As it was marked-out when the satellite image was taken, it's a max-size pitch. Of course it's easy to narrow a pitch - but not so easy to shorten it.
The I compared that with Pairc Tailteann (where we played Louth in last year's championship, and which Louth could have opted for again). It's 5 meters shorter, and the same width (though as I said, widths are easily changed).
Not sure this analysis amounts to anything of use - i.e. doubtful that that difference was a factor in the selection.
Interestingly the same method of measuring (not sure how accurate it is) has Croke Park 1.5m short of max length and 4m short of max width (and it looks to me like there isn't room to make it wider without moving the substitution-zone marking off the grass). I see Wikipedia has it larger (max length and 2m short on the width). But I used the same method to measure Inniskeen, and that method showed Inniskeen as max in both dimensions. Planning to storm Croke Park with a tape measure on the next visit! ;-)