I've always found that the neck thru basses have the better, slimmer feeling necks, even though the nut width is identical on nearly all models except the Dolphin 4 string. Even a newish Stage 1 feels fine, there is, as already mentioned still some variation in neck thickness in the same models thru the years. For me a Stage 1 4 string represents real good value if you look at the prices they are going for, unless you want a specific pick up set up such as the $$, I reckon it's worth trying to scrape together the extra dollar!!
I Dolphin 5, this has a nice neck, if anything the string spacing is a little too tight for me, the Dolpohin rnge seems to be the opposite of the Stage 1 basses, the Dolphin 4 has a wider nut than the Stage 1 4 string, yet the Stage 1 5 string goes down the broad neck route whilst the Dolphin is narrower.
Warwci now offer a custom neck profile thru their custom shop, it's a lot of $$ though. I spoke to a UK custom geezer a few years back who said it was real easy to shave warwick necks down so they feel a lot slimmer, it doesn't take a lot of wood, you just gotta know where to take it from!
Tony (waffling on a sunday morning)