Hi, I have been using a Multus for around a year now. I hadn't heard of the Cublex before, so I took a peek on Youtube.
To me, the biggest difference is one's a lathe that will mill, the other's a mill that can turn.(Sorry, too obvious?)
If you need 5 axis simultaneous machining you're out of luck with the Multus. The B axis (turret) is positioning only, not a "true" axis.
You can use a barfeeder with it (if you want), and hold much bigger billets as well.
We have the 2nd spindle so parts are transfered and finished completely.
Internal turning in the Cublex looked like the usual hassle of swarf staying in the part, because it's vertical.
What I like the most about the Multus is the Thermal Compensation really does work well.
About 20 deg celcius change in ambient temps here during the day and I don't have to warm it up, or chase tool offsets all day. In fact I didn't adjust anything at all today (it easily stayed within 0.02mm).
What I don't like are the terribly long tool changes, the weak turret coupling which can get knocked out of alignment at the drop of a hat, and IGF just plain sucks.
But a big part of your decision is, what support will you get from your supplier. All machines require a learning curve and can be frustrating. If you can get a question answered over the phone, or have someone come take a look, good.
If you have to wait for an answer from HQ or Japan (or can't get one at all), you might be spending a lot of time here at CNCzone!
So, Multus or Cublex? They look too different to me, apples and oranges.