I think the extra-long scale length will be fine for tuning to A440.
Scale length, string gauge and tuning are all highly inter-dependent elements that affect string tension. Increase scale length only and you increase string tension when tuned to A440. Increase string gauge only and you increase string tension at standard tuning. Drop your tuning down and you decrease string tension. So you can play these variables off one another to get the feel and sound you like.
Bass players have been using extended-scale basses for years. Some electric basses are 35" or 36" scale, and they have a great effect on feel and tone.
It's the same reason why an 8-foot grand piano sounds better than a little upright... the harmonics and overtones seem to ring more true on longer strings.
The longer scale length on the XL guitars allows you to either drop your tuning without things getting all sloppy in the lower register, or use lighter strings and still have good string tension and tight tone at standard tuning.
You're probably the best judge of whether the 27" scale is something that's right for you.