Material spec - Aluminium is notoriously variable in diameter when you buy it from your stockholder but general H9 spec for raw material. If you were running lots of aluminium I'd look at adaptive guide bush which automatically adjusts via air pressure to allow for variations in the bar.
Machines - All the Japanese manufactured machines are of good quality and although some are better than others IMO you're better seeing machines in the flesh and how you like to operate/program it. If you're new to swiss turning you'll need good service and programming backup to start off with so see how you get on with each dealer
Lights out running - If you run neat cutting oil on machine then its normal practice to fit fire extinguisher on machine wired into the machine shutdown procedure on activation. If part lends itself to it you can set up tool life monitoring either via control or write a macro. You'll also need high capacity finished parts storage so a parts conveyor or dedicated unloader to an external high capacity storage bin is a must. Also look at a chip conveyor to get rid of the chips from the tank during machining. Other things to consider are high pressure coolant for swarf control (for which you'll also need oil mist extractor) or if you can't stretch to this in your budget a subspindle coolant wash to clean sub collet out during pickoff
Good luck with whatever you decide