PTOEguy asked:
How hard is it to learn banjo after playing uke?
Really not difficult, once you get over the significantly larger fret spacings. The choice(s) you need to make are
4-string or 5-string and
which tuning. You can play a 5-string like a 4-string, just ignore the 5th string, or even remove it, but most 5-string banjos are "full length", 26+ inches scale length (nut to bridge), 22 frets. 4-string banjos are available in shorter scale lengths, eg. 17 and 19 frets ... I don't have a specific measurement to hand, but they'll be proportionally shorter.
However, if you want that "authentic bluegrass sound" you'll need a 5-string instrument 'cos you'll need the 5th drone string under your thumb for a lot of the picking.
As for tunings, the "standard" tuning for a "bluegrass" banjo is gDGBD, which is somewhat like the tuning often used on a baritone ukulele, but with the first string tuned down two semi-tones. It's quite acceptable to play a 5-string banjo tuned gDGBE, the same as a baritone ukulele or the top four strings on a guitar (I'm ignoring the 5th string for these comparasions), this is often termed "Chicago tuning". With this tuning all your familiar ukulele chord shapes can be used, they just have different names, however, you may have problems adapting bluegrass licks to suit this tuning ... confused yet
A four-string banjo will mostly be tuned in one of three ways, depending on the style of music that's being played and what the player is already used to, eg: DGBD and DGBE (as above), also CGDA (fifths), the same as a viola, which is similar to a fiddle or mandolin.
All of these are
HEAVY compared to a ukulele. Even coming from a background in playing jumbo guitars (around 2 kilos) my 5-string is noticably heavier at over 2.5 kilos, and that's an open-backed instrument, a resonator will be even more!
If you're at all serious, definitely try before you buy and try to find someone local who can impart a bit of advice.
And how much do I gain in terms of sound over a banjolele?
... lots ... and then some. A large pot banjo with steel strings and a resonator is
LOUD!