By the way, rather than say "if customer==b then..." better indirection is "if customer.hasFeatureX then...". However, one should wait until about 3 customers use that feature before making it a column.
Better is a relative term. By adding a new feature (or when changing it to a column from an IF) you've just made a branchable change in a monolithic file. Have A Nice Day, the build manager will be around to see you later today.

Whereas adding a new decryption algorithm/parser/whatever in my setup only affects that bit and that bit only.