The brown ones were better!

In terms of lifespan or the preheating of the electrodes?

I never saw the brown ones?, but I had loads of the green ones in service

Im yet to get a brown one but i have plenty of green ones with the brown pin inserts and tbh most of the ones i got are faulty lol. You flick the switch on and they wont do anything not even attempt to light the tube but if you switch them off and back on a few minuets later they will pre heat the tubes and light as normal and they do that all the time sometimes they work sometimes they wont do a thing????

Shaingout used the green one, inside the white cylinder of their Electronic-Start ballast: (...)

I've known a fair few of the green ones to suddenly just stop working. Usually they've not had much use either. Never had a brown one fail, they always seemed to last the life of the fitting.

Caps drying out? Some of these are probably getting on for 20-25 years old now?

I have had a brown cased one fail, it either wouldn't attempt to strike at all or would violently pulse the tube and cause the ballast to rumble, possibly damaged by an EOL tube left in for an extended time or as above dry caps, must have been in the fitting for 30 years though to be fair.
I've also had a couple of the green ones go, one was in one of those fittings with the starter directly under the tube cathode so it had been roasted for 10 years to be fair, but the other was rather poor and installed in my own Fitzgerald LP.40 for about 5 years so not at all hammered, but just randomly stopped working one day and never worked again.

I have noticed there are 2 "sorts" of green EFS600's the ones in the dark green cases which have indivudal tube wattages listed on them 30W-125W, I find these work well and give nice preheat and good striking action, but I have also noticed there are later EFS600's in lighter green cases that are just "4W-125W" rated and I find these dont work as well in that they will sort of "drag" a tube preheating it while trying to strike it at the same time and rumbling the ballast, I dont like those! but the earlier 30W-125W EFS600's I do like and have had zero problems with (wish I could find a few more!)

There does seem to have been a few variations over the years. I've also got a Durastart white cased starter somewhere, that one gives a really long preheat though does seem to be able to start some quite stubborn lamps