Hmm. Ive seen alot of problems out of the SIMM sockets used on the A4000 motherboards, though I never personally experienced any problems with the A4000T. I've never seen any problem with the A3000T ZIPP sockets either, and mine came from the factory fully populated with 18megs, an A3640, the Ramsey 7/DMAC 4, and a blank footprint where the 68030/68882 would have been soldered on the motherboard.
The A4000T which I had for several years, I did not buy new, and the previous owner had already installed an 060/50mhz accelerator with 64megs of VERY-FAST ram. I believe the SCSI controller was also on the accelerator, but I could not swear to it at this point, as its been quite a few years... I do remember that the system did have extremely good performance running Workbench 3.1 applications, especially when using graphics-card (CV-64) screen modes.. It really did "smoke the living dogsh!t" out of Wintels of many times it's processor clockspeed.
I never did alter the configuration of the A3000T. It was kind of a rare machine. It actually came from commodore with "A3000T-040" printed on the front panel. I sold this machine fairly recently (a couple of years ago). It's performance was roughly "on-the par" with some of the later 040/060 accelerated Macintosh machines.
Also, the A3000 scandoubler/de-interlacer is among the best overall quality Ive seen from such a device.
Anyone using either of the machines for any sort of serious application is most certainly going to have an accelerator, with memory of a much better performance spec than what's available on the motherboard or the Z-III bus. For the majority of High-end accelerators, the same can be said about the SCSI controller.
As others have mentioned, the A3000T is truly "built like a tank," and I am partial to case designs that reflect the original Commodore Styling. Not to say the A4000T was not a really kewl case design in comparisson to other full tower PC/server cases of the same era.
I am also very partial to machines that have socketed chips. I have had to replace 8520s, Paulas, Serial line driver/reciever chips etc. on various AMIGA models through the years due to lightning strikes, power surges, careless plugging/unplugging of cables, etc.. So, SMT soldered chips is not really one of the better features of the A1200/A4000 series of AMIGAs..
Welp, I can't think of anything else to directly compare.. Truth is, I loved both machines, and only "let go of them" because I knew they'd get more use by the people I sold them to then I was giving them. (and I drastically needed the space they were occupying for other things)
