Jack,
I don't know if the following info will be useful or not but here it is: I couldn't resist the price of the TC620X from Dixie Art so I bought one. My TC910 is working fine but, well, I just wanted a twin with tank so I now have both. Several days passed after my online order and I hadn't heard anything re shipping so I called Dixie Art. The service person looked up my order and told me that my compressor would be drop shipped from their distributor "Armadillo" and they would send a UPS tracking number as soon as they had one. Couple more days passed and I got an email from Dixie Art with a tracking number - my compressor was on the truck for delivery that day and I received it (from Armadillo) that afternoon. It was double packed in an outside box with paper packing around the actual SparMax box and no damage. About 6 days total. That was my experience with Dixie Art - just no hassle.
Now to the compressor. It's quite a bit heavier than the TC910 at about 24 lbs. It's attractive and similar to the TC910 except for the curved in case at the front and the additional gauge on the tank. It has two 1/8" BSP output connections so you can connect two ABs but not use them simultaniously. Mine came with two 10 ft hoses. I put it on the bench and did a little comparison with the TC910:
SparMax Badger
Time empty to full 28 sec 80 sec
Time cutoff to full 9 sec 28 sec
So the difference in output of the twin is obvious. And, to the little 1 inch diam. gauges. Yes, the markings seem to be weird: from 0-20 PSI the marks are at 5 PSI but above 20 they are at 2.5 PSI. Using tank pressure readings mine shuts off at 65 PSI and restarts at 40 PSI. The regulator and gauge are quite different though. If I set pressure at 20PSI with my H&S Evolution brush attached then depress the trigger pressure appears to drop about 8-10 PSI; If I set the pressure to 20PSI while the trigger is depressed, the pressure is rock steady until I release the trigger and the gauge immediately goes up about 8-10 PSI, pressing the trigger again and pressure drops in about 1/2 sec to the set 20PSI. My friends TC2000 behaves exactly the same so I believe its just 'the nature of the beast'. It does not bother ME but might bother some. What's happening at the AB is what's important and there are no pressure blasts and pulses regardless of what the darn little gauge says.
In terms of noise, I think it's bit quieter than the TC910 and noise doesn't change as pressure increases as it does with the TC910. The pump is mounted to the tank on 4 large hard rubber (?) gadgets which probably proabably absorb vibration and is one reason for the lower noise. The TC910 is bolted directly (metal to metal) to the tank.
Last, as far as difference in tank size (2.5 vs 3 L) I think it's of little practical difference. If my use of Boyle's Law is correct, the 2.5L tank holds10.2L of compressed air vs 11.6L of compressed air for the 3L tank.
In actual use, I doubt anyone could tell the difference except for the shorter filling times. Personally, I like both but if I had to choose I'd pick the SparMax.
Sorry for the long post but I hope it's useful.