Leap is supported by Cisco client card and other noncisco vendor who has leap licencse like airport card ....
If you have card which does not support leap I will say go for eap tls if you think
it is not process intensive ....if you fins it is very process intensive and too many steps to configre go for peap ...
Leap is light weigth , eap tls is high cpu intesive and peap comes in middle
of both .
with peap you have choise if you want to use microsoft peap supplicant or Cisco ...peap is alsoway to go ...It is admin decision which one is more suitable in their environment . .....
Peap uses username and password for client and cerificate for server so if you do not want to load certificate on each client peap is way to go ....
in eap tls both client and server needs certificate so each client needs certficate ....
Nilesh