This reply doesn’t give the MX400 much credit IMO. It is a mid-range multi FX hardware unit from 2006, and should be judged as such.
FX quality:
Comparing it to a VST is quite pointless, as it’s apples and oranges, and the OP has stated he is after a rack unit. The reverbs sound like a 2006 mid-range multi FX unit: not great, not terrible. Highly useful, IMO. You could buy a boutique reverb pedal and get amazing reverb, but then you won’t have a dual processing multi FX unit.
Interface:
Yes, the MX400 has menu diving. No surprise there, from a 1U rack unit with loads of parameters. The good news is, the menu diving is not so bad. I find it way more hands on compared to my Eventide H9 pedal, for instance. For each program, you can choose three parameters which are adjustable from the main screen. For more detailed control, you have to go into the menu.
Processing multi FX:
MasterLeader points out something important: when you set up two effects on one processing unit, you lose some of the control (and quality) from the individual effect (due to processing power). But if you should need dual effect with full processing power, this is still a dual processing unit, so you can set the two units in single mode, and feed one into the other.
Summary:
For €150, the MX400 has a lot to offer. Will you get a better quality unit with the X32? Sure, but it will also cost you 10 times as much. I have the MX400, and I’m happy with it. I’ll keep it until I can justify an upgrade.