I suppose my answer could be refined as:
o If you need an ATM solution, use the AIP card.
o If you merely want a DS-3 or slower point-to-point link between
two routers, test both solutions, (or talk to someone who has),
to determine which solution has better performance; or
o If you want a point-to-point connection between two routers at
speeds faster than HSSI can support (a bit more than 45 Mbps,
I think) use the AIP card.
Again, you should also consult your router vendor. They should be giving
you all this information and more. For example, you might discuss a
OC-3c IP over SONET solution for point-to-point connections.
I would suggest the POS card over the AIP card for a