To some extent what you intend to us ethe mill for will have a bearing one what is useful or not. Since I got a benchtop mill all my drilling has been done on that as it is a lot easier to accurately position holes as there is no need for marking out, punching and then locationg punch markes etc. So the bit of extra quil travel is useful as the mill becomes your main machine for drilling.
I would suggest that for any significant milling that you try and keep quill extension to a minumum as it helps with rigidity so in that case the longer travel will have less bearing. On lighter work say cutters below 3-4mm you are not going to be loading the machine much unless you get silly with depths of cut so in that case you can make use of the longer extension.
The SX2.7 (&L) also have the tapping feature which the others don’t. This can be useful if you tend to do a lot of tapping and it will cope with upto M10 and I would say don’t go smaller than M3 as there is no “feel” which may see smaller taps snap.
The SX2.7 (&L) has a fixed head where as the other two can tilt. In 20yrs of use and after making a lot of models I’ve never found the need to tilt the head, the work has always been able to be tilted and not all of those angled cuts could have easily been done with a tilt head but were easy with it kept vertical. The other thing with the tilt heads is that you need to watch the tram as a snatch can throw the head out and then you need to tram it all in again.
The Warco is a 2 speed machine so you will likely get some gear noise, the other two being single belt from motor to spindle will be quieter. Not sure if the Warco is brushed or brushless but the Brushles smotors have some more torque though the low ratio of the Warco may actually mean it has more spindle torque, hence the reason it can run a slightly lower wattage motor.
I think most members here would rate ARC as the nicest to deal with and of the other two I would go with Warco based on what I have bought from them in the past and what I have seen on the Amadeal stands when all used to go to shows.
If you have alook in the workshop section of the site you will find a few articles I wrote using a standard length table SX2.7 and from that if you look through my Youtube there are others there.