I’ve got a mains T12 as well. Honestly I haven’t bothered to assemble it yet as I’m unable to make myself happy enough with it to consider using it full time. The mods required to make it safe are extensive and I haven’t had the inclination to jump through the hoops. I think both handles suck. The 9501 handle’s strain relief keeps buggering off plus I’m getting intermittent problems with tip feedback which has caused it to blow two tips now. The default 936 style handle I haven’t tried extensively but the requirement to change tips occasionally makes it difficult to use as like the weller it requires partially dismantling.
Granted the T12 is objectively better than the weller in performance but not quality or reliability. If they fixed those issues, even for 2x the price it’d be a killer platform.
I wrote a list of requirements, including budget, and the metcal came out on top. Fast tip change, next day availability of all parts without postal buggery, very fast heat up and delivery, long tip lifespan, handle size, reliability, no fiddling around getting stuff working.
Edit: to note I’m keeping the DC T12. It was purchased for running off an SLA really. It will do the job for light duty work there.
Edit 2: tggzzz describes the above problems as fettling and that’s exactly what it is. This is an objective get work done and get out tool. I rather like making things and seeing the results more than playing fix the tools (test gear aside as that has some learning potential)