I have the Australian Vicmarc 300VL long bed (51") and would not trade for it for any other lathe out there. There are some differences in the two, I have turned on the CS version as well as mine. It is what you get used to, I am used to the Aussie version so that is my preference. And after turning on the short bed version and having to take the tailstock on and off, I am glad I got the longbed. I just move the tailstock down to the end and out of the way - saves the back. The tool post is 30mm on mine and 1" on the CS version. Both are stout, the 30mm (1 3/16) will take a little more abuse and not flex. After the controller and motor (mine is a 2hp vector controller), the biggest difference is the base.
Since you are building your own, you might want to take a look at the Australian version. The red bar across the front is an emergency kill switch, bump it with your knee and its the same as hitting stop. Also the front of the Vic base is more or less flat. It is angled back a few degrees, and the back is angled quit a bit compared to the front. But I am never on that side. This gives it a fairly wide foot print that is stable. There are no splayed legs to get in the way, and I can work around the headstock without tripping. I can use the CS base, but am not in love with it. Its as clumsy as a Oneway to me. There is also a chip chute built into the base that lets the shavings fall out the back.
Recently I have been roughing out 22" Pecan bowls. I core them and get around 5 to 6 bowls per blank. The mass (1000 lbs) of the 300VL was able to handle the blanks with no problem, from the rough log to the coring. I don't think you can go wrong with either lathe, just be sure to get a Vic chuck to go on your Vic lathe....
We also have a MIG welder. We bought a Millermatic 180 and its a great little tool. If you are getting a MIG, get the C25 gas version - 75% Argon 25% CO2. This is good for the steel you will be welding. For Aluminum all you have to do is change the gas and wire and you are in business. The wire for gas welding is about half that if the flux core wire. Figuring in the cost of the gas you are still ahead. Hobart is owned by Miller and a little lighter duty, be sure to read about their duty cycles. If you check around you can get the Millers at a decent price, not too much different than the Hobart. Either one is good, the Hobart is the consumer model and the Miller is the industrial. Also the bigger models like the 180 will weld thicker steel for down the road when you have to repair your trailer or build one.
And if you are going to work plate steel, look at a Miller plasma cutter. We bought the 375, which can do "shearing" cuts up to 5/8" - it does an excellent job on 3/8" and under. With some 1/4" MDF templates you can make miter cuts in angle iron. Just finished up doing that for a welding table a earlier this evening. Next year its a TIG welder, you just can't have enough "tools" before the time on this rock is over.....
Good luck with your Vic, you really can't go wrong with what you are doing.