but would you take a 4x10 + 1x15 over a 2x10 + 1x15?
There are very few, if any, 115's that have the SPL, power and punch and low end of a good quality 410.... that would be a misbalance to me in most cases.
IMO, the 115/210 stack made a lot of sense way back in the day when many of the 115 cabs were top end constrained, and many of the early 210 cabs were thin and nasally. This is not the case today IMO and IME.
That being said, every cab and every cab combination sounds different. I prefer the ease of a large 1 cab solution, and you don't deal with different SPL/balancing issues, etc. Pure personal taste there.
However, don't think that a 115/210 rig will have more bottom or volume than a 410... it might, it might not, depending on the brand/design, etc.
On a side not, if the Goliath IV you tried was an 8ohm cab, that would explain it right there. Since the 350x is a low powered head (and sounds even lower power to me than its spec suggests) running that head at 8ohms results in VERY little power going into that Goliath.