I would say it compares very well to Pointools - they are not identical, but do much the same stuff, just slightly differently. I would recommend it, and will talk through my experiences below. There are no other alternatives so far as I know, but it’s a great plugin in its own right, not just because there is nothing else.
I too was dismayed by the stopping of development with Pointools, as I had not long bought the Pointools Suite when it was sold and development petered out (significantly it was before they released the 64 bit version of the Rhino plugin that I had been told was being worked on).
With Pointools no longer being developed, and only running on 32 bit Rhino, and really only successfully in Rhino 4, I was very excited to hear that the Arena4D plugin was going to be available in April. It’s only £500 plus VAT, so I bought a license.
Veesus have put a lot of work into developing the Arena4D plugin since releasing it around April 2015 - it is now on v 1.9, and they have all been significant releases.
I carried on using Pointools for a few months until the Arena4D plugin had as much functionality as I needed (ie very similar to Pointools), and have been using it exclusively, except for old projects, since September.
The Arena4D .VPC files are larger than Pointools .POD files, but are a comparable in size to other bespoke pointcloud files, and still significantly smaller than the .PTS equivalents. The speed is a bit slower, but nothing significant, but then nothing else, as far as I am aware, has really come close to the speed of Pointools. The downside with Pointools was sometimes that the data was not refreshed, which has never been a problem with Arena4D. I also have the main Pointools desktop program, to slice up the data, and this also suffered, fairly frequently, from data loss when exporting chunks, which you might not notice until later, or not at all and just think you had some inadequate scanning on your hands. The Arena4D equivalent has not had that problem.
I also had fairly frequent crashes with Pointools - it seemed to be something to do with the OpenGL viewport getting out of sync between Rhino and the Pointools engine, and freezing, and requiring a restart. This happened every couple of hours on a bad day, but sometimes not for a few days. Pointools never got to the bottom of the problem for me, I just had to live with it and save frequently. I’ve not had any similar problems with Arena4D, but I had a problem around August where Rhino would slow down after using it with Arena4D for a couple of hours - Veesus had already fixed this by the time I reported it, and they let me have a beta until the fix was released as a main version. I can’t say I ever got anything near that level of support from Pointools.
I’m very happy with the Arena4D plugin, it works with Rhino 5 64 bit, and you’'l get great support.
If you want to try it, they have recently increased the trial time to 20 minutes (this is reset every time you restart Rhino, so you can have multiple goes with it, albeit in 20 minute chunks). The main desktop program, Data Studio, can also be used to import data after your trial of that expires. Otherwise, it has similar functionality to the Pointools equivalent, but with much more GIS integration.
Hope this is helpful, let me know if you have any queries and I’ll try to help,