I have the Stradic 4000 and a 2016 Biomaster SW 6000 XG (from Digitaka, in Japan, as you can't get the 6000 size in NZ or Australia).
The Biomaster is a quite a bit more grunty than a 5000 - reflected in the higher drag rating, and the extra 120g or so in weight.
I presume you're either importing the Biomaster or buying it second hand, if it's the 2013 model?
I use the Stradic for my heavier soft baiting, and it's a lovely reel for that. Smooth drag. And the Biomaster for light top water.
The Biomasters are slightly faster retrieve than the equivalent Stradic, which is a bit of an advantage for lure fishing i think.
You are probably aware the 4000 and 5000 are the same reel, but with a slightly bigger spool giving more capacity and faster retrieve.