I always use the same 3 systems. Boarding, cloaking, and mind control.

Why?

It's reliable: If you use weapons, you have to worry about finding the good ones. This might mean having to buy one at a store since weapons usually don't drop from combat/events. The same applies to drones. This compared to cloaking/mind control/boarding. There are no add-ons necessary to use the system, so it's always guaranteed to do exactly what you want.

It's cheap: All 3 of those systems max out at level 3. Much cheaper than say weapons or drones, again because you'd also have to buy the upgrades and weapons/drones necessary. Also, since your strategy uses no drones/missles and their parts for extra scrap. For boarding, crew members usually accumulate naturally through events, so you don't have to worry about buying any.

It's reliable: Since your strategy uses no missles/drones, you don't have to worry about running out of anything. If you have mantis crew member, it makes your boarding stronger, and if you stack this with mind control, you can always win. Cloaking also is useful for avoiding damage. Hacking can used as well, but it requires drone parts and if the enemy has a defense drone, hacking can't really be used.

If you get an emergency respirator/ lanius, you can use boarding against drones.

This strategy is so good, I've gotten to sector 8 with just a heavy laser. I rarely ever upgrade my weapon system just because I never need them.

Also, is mind control useful? Yes. It has the most blue options of any system. It's an obvious counter to mind control. It can be used to stop enemies from repairing, kill enemy crew(obviously), and it can be used to distract enemies. For example, if you mind control an enemy in shields, and then board weapons. The enemy crew will go for shields since it has higher priority. As a result you'll be able to take down enemy weapons with little resistance. Also, usually at least 1 enemy crew will be killed from mind control.