2254c vs Mixbuzz1 vs SB4000 vs API 2500 for Mixbuss duties?

Anyone would like to comment on these?

Still trying to figure out what unit for permanent mixbuss duties?

Which DIY unit was easier to build?

ALL of them  , easier 'maybe" SB4000

I built the 33609, which is similar to the 2254c. I've never used an API 2500, and I haven't finished building a SSL clone, but I have a MixBuzz in the works. I recently compared the Pico compressor to the 33609 (plus a few other compressors) and found that the 33609 provided a noticeable change to the quality of the sound. On acoustic guitar, it brought out the attack, made it harmonically big and warm. The Pico did not do this, but rather, brought the bus together in a warm way, but did not have a noticeable coloring of the sound. So, for use on a mix buss, I would not think the Neve's would often be chosen. More often a transparent compressor, like some of the others you mention. 
I will probably post some sound samples from these compressors at some point if you are interested.

That would be great DMP, thanks 

i recently made an SB4000 and im literally blown away by its versatility.
it can be soft and clean (dont want to sat transparent because its not but in the best possible way)
but it can also be thick and dirty making it a general bus compressor king!
sort and subtle for the mix but filthy andoshy for parrallel drum busses and also just generally amazing on anything with a pokey transient.
Ive never made anything before and i managed to make it in 8 days....8 DAYS people!!!
I can defo say that its a great addition to the mix if you are looking for something that will add a certain character like a glue.

+2 for the SB4000

I'm fairly new at DIY'ing, and the only trouble I had was the ribbon cable assembly. The ribbon cable headers are FAR easier to "connect" to the ribbon itself (just align the cable with the teeth and use a drill press to clamp down. the top automatically locks into place... brilliant!), but for some reason I made it more difficult on myself and broke a few. The PCB has a shit ton of components, so be sure to test/identify each and you're good to go. Not hard by any means. And Mike's build documentation is very detailed; it covers all the necessary wiring and such.

The sound is IMO more on the transparent side. I like my compressors to be an "effect", not just a leveling device. However, the SB4000 can do transparent OR squooshy/gooey/yummy. Right now I'm using Ratio @ 10:1, Attack @ 3ms, Release @ 600ms, SCF @ Tilt 2 as my starting point for the mix bus. The Side-chain Filters make this compressor EXTREMELY versatile. I say this is the one to start with!

Sound samples please

dtrax recently f'd up the ribbon cable for the sb4000 was able to use a computer interconnect cable (side cutter pliers down to size worked great cheap fix $5.