Latency spikes, probably. But most UIs shouldn't be churning through enough allocations to lead to noticeable GC pauses, and not all of today's GCs have major problems with pause times.
I don't think Electron's problems are that simple.
From a non expert point of view, it’s about bringing in so much dead code. Like support for every os audio subsystem for a graphic app, or the whole sandboxing thing while you’re already accessing files and running scripts. Or even the table and float layout while everything is using flex. All those things need to be initialized and hooked up. At least Cordova (mobile) runs only on the system web engine which was already slimmed down.
I work on an Electron app, and we have a ticket open to investigate why the heck it's asking the OS for Bluetooth permissions even though we'd never use it. There are, of course, higher priority things to get to first, bugs that have larger effects. I'd love to be able to get to that one…
I don't think Electron's problems are that simple.