Welectron's pricing is competitive with others, but the part I appreciate the most is that you can easily add the carrying case, fuses, magnet and other accessories specific to that model when adding it to your cart.
When I bought mine they didn't have the exact combination in stock so they wrote to me and asked if it was OK to cobble one together from two different kits to avoid the wait, that the box wouldn't be sealed when it arrived.
(I said yes, obviously...)
I've never seen an official Brymen kit, just the DMM with test leads and maybe temp. probes, etc. and then the reseller adds any additional accessories if you add them to your order. If you're referring to a Dave-Brymen product then that could be different. I have actually not seen any carrying cases on Dave's site for a year or so, but Welectron has them, not sure what the story is on that.
There is a specific carrying case for the BM78x series. It's slightly narrower and thinner than the carrying case for the BM869s, for example.
I also don't see the original BM235 carrying case, the one with the silkscreened letters. It's ever so slightly thinner than the 121GW carrying case.
Personally, I always order the appropriate carrying case with my handheld DMMs. Keeps all the parts together, and I can just grab and go.