PEAPv0, PEAPv1 and TTLS have the same security properties.
PEAP is a SSL wrapper around EAP carrying EAP.
TTLS is a SSL wrapper around diameter TLVs carrying RADIUS authentication attributes.
EAP-TTLS-PAP can be useful over EAP-PEAP if backend authentication database store credentials in a non-reversable hash format such as bigcrypt or any form not compatible with MSCHAP (NT-OWF) In this case it is not possible to authenticate using any of the CHAP based methods.
While you could also emulate PAP using EAP-PEAPv1-GTC this is not as widely supported by clients.
PEAP has some added baggage over TTLS in the form of PEAP version negotiation headaches and historical incompatibilities in PEAPv1 (Such as client magic when deriving master key from PRF) which have made their way into early implementations.
I normally see EAP-TTLS implemented in embedded clients such as subscriber modules in wireless gear with PEAP used more by laptop computers and mobile handsets.
EAP-TTLS has historically not been supported in Windows clients without having to install third party software. EAP-TTLS is now supported starting with Windows 8.
Some additional thoughts:
EAP-TTLS was invented by a RADIUS vendor.
EAP-PEAPv0 was invented by Microsoft.
EAP-PEAPv1 came out of the IETF process.
There was some additional IETF work on a PEAPv2 which would have made the system more secure by way of crypto bindings to inner authentication methods. This has not gone anywhere as near as I can tell.