[gerthworm]

Very much depends on the game, your strategy, and how effectively your driver can use both speeds.

For Stronghold, our bot had two-speed gearboxes on the drivetrain. We mostly stayed in low gear, which had the ratios optimized around pushing, fine maneuvering (shot alignment), and defense crossing. We also had a high gear for sprinting across the field. From our post-match data gathering, it looked like our driver only stayed in high gear ~5% of the time, but it did help us win a few races to boulders.

Additionally, we put some protection logic in software to monitor the current draw from the battery while in high gear. If it exceeded a threshold for too long, we'd force the bot into low gear regardless of driver command.

For strategies & games where you don't have a reason to need both, it's probably not worth the complexity (and weight and size). Recycle rush is an example of a game where it probably didn't make sense for most teams to do two-speed.

Advantages:
-- Two speed ranges reduces some tradeoffs during drivetrain design
-- Potential for getting fine maneuvering, pushing power, and speed all at once
-- Gives drivers more options for during-game strategy

Disadvantages:
-- Heaver, larger, more expensive, more points of failure, more complex software
-- Robust operation usually needs pneumatic system, or fairly chunky servos
-- Requires more input from driver (unless you write some beastly software)