I think these new nodes are still pretty lightly used, give it a few months and then do a comparison. Benchmarking VPS/cloud instances can be tricky since you might be on a quite node or a heavily utilized node. You really need to provision many machines and run the checks at random times over a period and then average the scores out.
I upgraded some of my VMs and they all failed to boot on their own and I had to manually boot each one after the migration.
I don't think MB/sec/dollar makes sense simply because disk speed does not scale. If you need a (very) fast disk, Linode is obviously the better choice.
Thats not the issue. The issue is if (and only if) you have a perfectly parallelizable task, you would be better off getting 4 x $5 DO servers with a rate of (4 x 287) 1148 MB/sec which is much better than 816 MB/sec for the same price. Or you could even get 3 $5 servers and have a rate of (3 x 287) 861 MB/sec which is still better and also cheaper.