If your thinking about it I would go for the 20". I have a 14x20 bass and love it. I also have a 16x18 floor tom I converted to bass and have had a lot of complements. Maybe it's the added 2 inches of depth in a 18" shell that helps, I don't know.
Personally I think the 20" bass is so much more versatile and has a sweater tone. My 18" bass is lacking out doors so I used my 16x22 when I needed to play an outdoor gig, until I recently received the 20". And looking at the picture supplied, the 20 is not going to increase your over all foot print.
Keeping everyone updated. On Monday I will get to try a vintage Gretsch 18x14 and a 20x14 side by side. Not quite the same as a new USA Custom but it will have to do. ATM leaning toward the 20x14 but let’s see.