Hi,
1) Yes, have been using Mach4 for a little over 2-1/2 years.
2) Yes, Mach4 can handle six coordinated axes (plus Out-of-Band axes as well up to a total of 32 motors).
3) Both Industrial AND Hobby handle probing identically.
and the industrial only having preparation for installing macros from companies that sell probes.
I've never heard of that.
The only feature that Industrial offers that Hobby does not
is Macro B programming. It has some application in industrial programs, things like conditional Gcode and stuff like
that. Have a look at Cbyrdtoppers (Mach4 board) description of how he used it for his grinding machine. If you have
been using Mach3 and it works for you then you wont need (or miss) macro B. The real advantage of Industrial is
SUPPORT. You ring NFS and you go to the top of the queue.
I am not aware of anything that obligates you to buy
Industrial but note that the Industrial licence applies to ONE machine only. Hobby on the other hand can be used
on up to five machines. It might be worthwhile explaining your situation to NFS. It may not be unreasonable to start
with Hobby and if it goes well for you then get Industrial, maybe NFS can do some sort of upgrade?
4) With either Hobby OR Industrial you need a good controller. Remember that the controller handles ALL the realtime
functions so no matter how good Mach is (or isn't) the controller determines how the machine will behave.
I personally prefer the Ethernet Smoothstepper by Warp9 TD. It is moderately priced ($190), not the cheapest but not
the dearest either. Just recently a number of new realtime features have been added (backlash comp, lathe threading,
and encoder driven PID spindle control). The long awaited THC feature is due to be released in a few days. That makes
the ESS the most up-to-date controller in the moderate price bracket.
Other worthy contenders are the 57CNC by PoKeys, the PMDX-424 by PMDX, the UC300 by CNCDrive.
One of the more expensive ($600) offerings is the Hicon by VitalSystems. It has always enjoyed an reputation of having
well developed realtime features. Until just recently it was the only controller to offer realtime THC for instance.
Another extremely high quality offering are the motion controllers offered by Galil. For four axes they start at about $2000.
The Galil, Hicon, PMDX-424 and probably the 57CNC don't require a BoB whereas the ESS and UC300 do. I would recommend
the modestly priced ($23) C11, one only for a simple machine but two (or more) adds much more IO. You will have to make
a few simple additional circuits to 'flesh the C11 out', or buy a more expensive BoB. CNCRoom does an MB2 especially for
the ESS, all three ports are developed to be used and connected to the outside world. It is about $200.
5) I use a dual core (1.8 GHz) Atom mini-ITX board, with NO graphics card. Its a really low powered board but it works really
well. Its
slow if I load really big etching files (10M plus) but once it loads and draws the toolpath it goes great guns
thereafter. The real advantage of using an external controller is that just about any 'cheap as chips' PC will work. Check
this little sucker out:
https://www.dfrobot.com/product-1585.html$209 with 4G/64G and Windows 10 Enterpise already loaded.....hard to beat that value and less than 4 inches square!
To accommodate Mach alone Windows 10 with 4G RAM and 64G hard drive would be ample. A graphics card is recommended
but I don't have one on my machine so I hardly rate it as essential. i3 or i5 is any amount for Mach.
If you want to load CAD/CAM on the same PC

then up the ante in the processor/memory/HDD/SSD/graphics to suit,
Mach doesn't require it but CAD/CAM do.
Craig