cost, cost of development, cost of maintenance, cost of running, cost of set, total cost of ownership
timing of phases of project (how quick to market)
ease of development traded off against quality of development
lifetime of project
availability of staff, quality of staff
vulnerability to attack, degree security, degree of security inbuilt to environment
the type of application (does it need monsterous servers or does it run on small discrete boxes), is the application going to grow, how flexible is the development, how easily does it scale
is it a corporate flagship (some people 'know' that Oracle is THE best database and therefore insist their company must run Oracle to demonstrate they are a top notch company. some people disparage the loke of PHP because its seen as not a 'real' / serious app tool.