So after listening to the XL for a lil while i have come up with this.
1. It has a more rich/ full sound compared to the BTL
2. It picks up lower notes and sounds better doing it but the BTL had more output on the lows.
3. on the higher side i think the BLT was a lil more versatile
4. anywhere in between this the XL killed it lol def is louder than the BTL in this range.
I would like to build a new box just to see if there is any difference, id like to build it to specs used by other member and who have seen good results.