Is it worth replacing globe valve with ball valve for my main shutoff?
YES!   I came across a 10:1 flow rate differential between 3/4 ball (25 GPM) and 1/2 globe (2.2 GPM)  There's almost a 50% reduction, just going from 3/4 pipe to 1/2 pipe (I inferred the pipe size flow differential by comparing 1/2" and 3/4" ball valves of the same type here).  Table 2 here Compares 2" ball at 228 and a globe at 44 for a ratio of 5:1, then add in pipe diameter and 10:1 seems reasonable.

Be sure they put in a full port ball valve in bronze with drain (on house side).
Full port has the least flow restriction.  Bronze is safe for potable water, the drain is for future repairs to drain the lines.