Hello Jake,
As a Proud owner of a B.C.A mk3 and an Axminster sx2 mini mill(very similar machine to the wm12) , I would say get the B.C.A. Providing it is tooled up and in a good mechanical condition.
Do you know if it is a MK2 or MK3?
This has a major impact on the table travels, It seems Clive had a Mk2 and comments on the work envelope being small. MK3 machines gained I believe 1 to 2" of travel on all slides which may not sound a lot but I have bored out a Land rover series 2a front wheel hub, wheel studs holes. Okay the clamping arraignment was a bit heath Robinson but I did not know at the time the centre hole of the table is threaded!
The capacity I suppose I haven't struggled with as I do own all the original spindle tooling which does seem to help a lot. The front hub I used the "Tenga" type small boring head, which equipped with a carbide tool chomped though the cast iron and weld without any complaints.
The worries people have for them being more a drilling machine are not really valid in my opinion, for hobby use, I'am able to achieve a higher depth of cut on the BCA than on my mini mill! The spindle set up is key to this, I set mine up in the dead of night to actually hear the oil squidging about with me swinging off it! Not scientific I know but boy what a difference it made to the depth of cuts. Yes in a industrial production environment they are not a mill, but for hobby use you ain't going to wear it out.
This is where I have to confess to owning 2 BCAs, My first one is in a rather used condition, which was staring me in the face when I went to view it but I had been rather excited buy the full set of spindle tooling and purchased it anyway! My second machine is mint, all original hand scraping on all the ways etc. Although this has very little in the way of tooling in comparison to my first. The first machine had come straight from industry to my workshop, (mid seventies to 2018) the second machine despite being older (mid sixties) took an early retirement in the early 90s and made 1 clock in 25 years!
What I am saying is tooling made the worn out machine worth it as I had to fight the machine very little, tightening up on the extremities of travel was just something I had to live with. Coming from the mini mill which I found frustrating to use due to the lack of quality control. The worn BCA made my milling jobs something to look forward too!
You say you have been brought up on Bridgeports, I being an apprentice being brought up on Bridgeports at exactly the same time as learning the BCA I haven't found any problems switching between the 2 types of machine if anything I am more adaptable at work because of having to be creative with set ups on the BCA at home!
The collet issue is an important one to make, early machines use 3/8X26tpi on spindle tooling MK3s use M9x1mm the dimension everywhere else are exactly the same! so take a not of the bottom of the drawbar some people have forced incorrect era of tooling in the drawbars which does wreck them (obviously!) The threaded collet issue is important aswell Internal threaded collets were only avaliable in 6mm, 1/4", 3/8" and 10mm if you have them you are well set up! I made up a 6mm and 1/4" fc3/weldon/side lock shank arbors that go directly in the spindle which I use all the time. I intend to make other sizes when time allows.
you also mention you have a small workshop, neither machines are big so your fine on that front however there is a vast chasm between the machine weights the BCA is extremely heavy so just expect that when it comes to moving it!
If you look through my albums there is one or 2 pictures which show my machine in action
I hope that makes sense
William