Good morning gamers,
There might not be a single faction in Star Wars Legion that has a go-to Corps unit choice like the Separatists do. Yes, you will see lists that feature six Geonosian Warrior squads (or fewer than six in a Rapid Interdiction Force battle force list) or six or seven B2 Battle Droids with Poggle the Lesser, but by and large, if you're playing against a Separatist player, it's only natural to expect to see several units of B1 Battle Droids in their army. Yes, these are iconic prequel trilogy units for the Trade Federation/Separatists, but they're also fabulous units in Legion. Let's see what they do and why everyone seems to be keen to take them.
B1 Battle Droids: The Profile
When my son and I got started playing Legion . . . we both hated B1s. I was playing Republic and my son was playing Separatists and the Republic units were durable while the B1s were . . . well, easy to squish and didn't do a lot of damage, no matter what you put in their unit to help them out. This was before the current version of Legion and the release of the "super size squad" personnel option, but even today, B1s aren't paying for a good profile. On offense, these guys roll 1 white die each and can't surge natively - that's bad. They roll 1 white defense die that also doesn't surge natively - and that's bad too. Each model has 1 wound, the unit has Courage 1, and they're a normal speed-2 . . . there's seemingly nothing to recommend this profile.
Except the cost - and in some respects, the special rules. Because their profile is so bad, their cost is incredibly low at 38 points (lower than any other Corps unit in the game). They have AI: Attack, which has both positive and negative ramifications, based on whether you're suppressed or not and whether or not you have an order token. If you don't have an order token and the unit is suppressed (which will usually be the case if they've taken 1-3 suppression tokens), the first action they have to take is an Attack action . . . which might not be the worst thing in the world, but also might not be what you want to do with them. As we'll see below, though, there are MANY ways to work around this, not least of which is having Courage 3 commanders in your list or access to Override.
They also have Coordinate: Droid Trooper, which has always been the reason to take B1s in your army - issuing an order to one of them likely means you have an order on ALL of them, so long as each squad has at least one model within range-1 of each other. While you can certainly do "chains" of B1s this way, a "web" of B1s is far more reliable at keeping the order control going - and it helps if you have another Droid Trooper (either a Droid Commander/Operative who started the chain and is near the end of the chain or a combat-oriented unit that's operating near the B1s) at the actual end, so they can benefit from the last coordinate. The only units that are unlikely to benefit from this chaining are your vehicles and Force Users (and geo-bugs, I guess), so they will be dependent on your command card to make sure they get the orders they want. Still, if all of your Corps units are B1 Battle Droids (or up to 1 of them is a Droid Trooper/has access to Direct from someone else), you shouldn't have any Corps units in your order pool, which helps with order efficiency and reliability a TON.