Why 100 people is rarely two 50-seaters
The arithmetic says two 50-seat coaches. The arithmetic is almost always wrong, for four reasons that have nothing to do with rates.
Nobody travels at 100% load. Between last-minute leave, people driving themselves and the two colleagues joining from Mysore, a 100-person offsite moves 86 to 92 people. Two 50-seaters leave with 15 empty seats you paid for at the top of the band.
Pickups are not in one place. A Bengaluru company of 100 has people in Whitefield, on the southern ORR and in Electronic City. One coach collecting all three means the first person aboard sits for 90 minutes before the bus leaves the city. Three smaller vehicles running three loops get everyone to the destination at the same time and each passenger travels an hour less.
Resorts have parking limits. Chikmagalur and Coorg estate properties routinely have room for two coaches and no more, and their access tracks defeat a twelve-metre vehicle entirely. Four 33-seaters are frequently more welcome at the far end than two 50-seaters.
Failure is not graceful. If one of two coaches breaks down, half your offsite is stranded. If one of four minibuses does, a quarter is, and the other three can double back. On a 200-person offsite we always plan an odd vehicle in the mix for exactly this reason.
The counter-argument is real too: more vehicles means more drivers to brief, more manifests and more parking. Above about six vehicles a convoy stops being manageable without a dedicated coordinator, which we provide on any movement of that size.