I much prefer the looks of a drum, and in the rear it doesn't really matter. Except on an Enfield. I had my rear brake lock up on my 2013 B5 Bullet around 6500 miles. Fortunately I was turning into a parking lot, and didn't crash. The pedal felt "different" when this happened. I was able to almost completely loosen the adjusting nut, and get the wheel turning again. It finished off the chain. It was actually twisted slightly. I wish RE would discover metal. I rode a couple of miles home, and the next day I took it apart and found out what had happened. The radius of the shoes was larger than the radius of the drum. The whole time I had it, only the very ends of the shoes were touching the drum. I wondered why it performed so badly. Finally, all the lining had broken off the ends of both shoes, allowing metal to metal contact between the drum and brake shoe backing plate, locking it up. The drum was full of bits of brake lining. I rode it a couple thousand miles with no rear brake (no issues, you have to get used to having very little brakes when riding an older Enfield anyway)Finally I decided to fix it, or try to. I sent several emails back and forth to Hitchcock's in the UK explaining the issue. They said they had seen this issue before, but it was not common. Apparently some older Enfield models had larger drums, I don't know if that was in the front or rear. They assured me they had the right parts for my bike so I ordered them. Sure enough they fit. It seems as though RE just uses parts they have laying around to build bikes out of. Actually that was one of only a few problems I had past 10,000 miles. But I rarely rode it above an indicated 55 mph.
So since my rear brake works fairly decent now (you don't want an easy to lock up rear brake) I would still prefer the drum. I would even like to get a drum for the front. I have no idea if that is possible or not. The old Iron Barrels made do with them.
As for ABS, the first thing I would do is disconnect it anyway. I do not ride bikes with computers. I have 6 bikes and none of them have computers. The RE was the first bike I ever bought with EFI, and I wasted no time in ditching that for an Amal carburetor setup with a conversion kit from Hitchcock's. It cost at least $100 less than a new fuel pump for the EFI system, and it runs 10 times better. The carb fattened everything up, it now pulls harder instead of wheezing, and throttle response is much better. Along with the aftermarket peashooter style pipe I put on it, without the baffle, it now sounds and feels much more powerful. It now has that THUMP THUMP THUMP that an Enfield should have instead of sounding like a sewing machine.
I will recommend a B5 if you want a vintage bike instead of a smooth quiet "modern" bike. I doubt the carb conversion kit is available for the new Euro model. Your only choice is a $500 electronic tuner, but I highly recommend it. The bike is set WAY too lean from the factory. And if you want it to sound right, you will need an aftermarket cat free exhaust. This is NOT a freeway bike unless you can ride 55-60 mph. Mine overheated badly in town with the EFI setup, to the point where the clutch wouldn't fully disengage. After going to the richer carburetor, that problem mostly went away. I can now ride through many miles of stop and go traffic without it overheating. And after 10,000+ miles, the shifting is buttery smooth.
Common problems on mine were:
1. The rear tire chewed it's way through the wiring harness to the rear lights. I repaired the harness and routed it above the fender.
2. The exhaust header nuts kept coming loose. I finally replaced them with bolts, drilled and safety wired. No more problems.
3. Battery cable ends broke off. I replaced the end on the positive cable, and completely replaced the negative cable.
4. If they still come with non maintenance free batteries, you will want to replace that. Mine only lasted 2 months anyway.
5. My headstay broke. I replaced it with an aftermarket one, which is much stronger. These bikes are shakers.
6 .Not a failure, but would have been eventually. The rear tank mounts do not line up with the holes in the frame. When you install the bolt and tighten it, it bends the rear tank mounts, and they will likely eventually break off. I used several fender washers on both sides to line everything up properly. It still has no rubber rear mount, but Sportsters don't either, and they vibrate even more.
7. The afore mentioned brake problem, which hopefully you won't have. Once sorted out, these bikes tend to be almost trouble free, as long as you respect their limits and don't push them. If you want to ride like a Japanese bike, I would get a Himalayan or one of the new twins. The basic design of the Bullet dates back to the '50s.