Another difference with the Will Lee is that (at least on the NYC models), the bass comes with a drop-D tuner, a feature I've never had on a bass before but suddenly found myself using on a gig the other night. I'm not sure if the metros will have that or not.
I'm looking at picking up a 4 string to mess with (only playing 5s for the past decade +), and one candidate has a D-tuner. For the life of me I can't see how I'd incorporate that. Do you drop at the beginning of a tune and then transpose notes on the fly, or just grab it for a short section of a tune or ? My brain cannot process such variables