Branches are bad, long branches of varying lengths are worse.

As reminder, every time you branch, you split the mainline frequency. Every 3 minutes on the main line turns into every 12 if you've got 4 branches and you're feeding them equally. If they get high ridership, you can further than run into the Green Line situation where it is physically impossible to stuff more trains into your mainline and so you can't raise branch frequencies further.

Beyond that, the longer the branch the harder it is to feed the trains into the mainline in their intended scheduling/order - there's more that can "go wrong"/vary.