Thanks for your answer xuweixu.
My setup is a MacBook Pro mid-2014, OSX 10.12.6, 16 GB RAM, an external raided 4TB SSD for samples, a 1TB SSD for recording, all disks working optimally according to DiskWarrior. I've been able to run entire sampled orchestral setups with effects without glitches on S1 v.3, and AFAIK i get no glitches when recording in the latest Logic or Pro Tools 11 HD.
The recording dropout issue is something that's happened lately, on v.4.x. It could well be related to the introduction of the low latency recording mode - that's great for VI's. But given my setup I think there should be a way to minimize dropout protection (which intermittently stops to buffer, causing the tempo/ recording disruptions) in favour of keeping the tempo/ recording going. Any suggestions?
I think dropout protection, by default, should be disabled as soon as you record. But before that's implemented any suggestions are more than welcome. Thanks!