I've built and flown quite a few aircraft in my day, all pattern airplanes except my first trainer. My last 2 designs (2 Piorun Eclipses and 2 Marsden Legend 3s) had plug-in wings. In the end, I much prefer the plug-in wing option with some advantages being:
-great adjustabily during building and flight trimming assuming you use wing adjusters;
-a lot more room available in the fuselage interior for radio etc;
-2 smaller panels = a bit easier for transport. I use wing bags.

Disadvantages include:
-greater complexity during construction phase. The kit producer has to have his *%@# together because properly boring the wing tube holes is critical;
-dihedral adjustments are not much of an option. You can always take a hacksaw and epoxy to a 1 piece wing to make any required adjustments.

Related to this is the plug-in stab option. Not quite as pretty as an integral stab with nice fillets but for aircraft transport or shipping/airline travel, the fuse gets much lot smaller when you remove the stabs.

Anyway, those are my preferences.