The speed density/bank fire systems work well - if you don't change much. The range of adjustment in the ECU is fairly small as it assumes it knows how much air was just ingested at a given RPM with a given throttle opening. So if you change the cam, or the intake, or the exhaust it won't really know and it may not be able to adjust far enough to make it work correctly.
That's where the mass airflow (MAF) systems come in. They don't assume, they measure. So then they can do the math to determine how much fuel is needed, and they have a table that tells them how long to open the injectors to get that much fuel. But they monitor the output via the O2 level and learn how much to adjust from their table to get the right amount of fuel and, therefore, the AFR they are supposed to be at. And it is that learning that you lose when you pull the battery.
Gary, AKA "Gary fellow":
Profile
Dad's: '81 F150 Ranger XLT 4x4: Down for restomod: Full-roller "stroked 351M" w/Trick Flow heads & intake, EEC-V SEFI/E4OD/3.50 gears w/Kevlar clutches
Blue: 2015 F150 Platinum 4x4 SuperCrew wearing Blue Jeans & sporting a 3.5L EB & Max Tow
Big Blue: 1985 F250HD 4x4: 460/ZF5/3.55's, D60 w/Ox locker & 10.25 Sterling/Trutrac, Blue Top & Borgeson, & EEC-V MAF/SEFI