Quoted from Pinash:
I've had some WPC games with spade connectors on the solenoids. I thought it was pretty handy.
It is, but they fall off over time. Those spade connectors were used on the latest wpc95 and pin2000 machines for speed of assembly, not for long term reliability. Spade connectors really suck I've grown to hate them as they lose tension and pull off connectors all the time at work (not pinball, though) They used to be good but it's hard to find a good brand anymore.
If you think you have to pull the assembly it's on into/out of the machine a lot, by all means, add a connector for ease of removal/assembly. Location machine you're servicing, high usage, high wear, etc.
For home use how often are you REALLY going to pull out that entire assembly once you rebuild it? For instance.... outhole coil assembly on old games. Those are annoying because the wire comes through the PF and then gets soldered.
One you do your initial rebuild on this area, it's going to be decades before you have to do it again (unless you did it wrong), if ever. Clean everything well, new coil sleeve, maybe new spring, teflon lube on the metal to metal junction, done. If it gums up you used too much lube.
Drop target mechs would be the worst offenders and probably should have connectors on them, it is usually easier to have the assembly on the bench/flat surface for replacement of drops.