IIRC it was possible to couch with throwing lance in secondary mode. So, you'll have more chances to kill something with your lances on horseback. And yes, it's possible to kill with couch even with 1 wpf in pole.
On the other hand you'll be easy prey for any dedicated horseman. Think about 1-2 lances and 2 packs of throwing daggers. With your 7 PT daggers can help you to dismount enemy horsemans and not to worry about some misses.
IMHO rouncey is better choice. More health, more charge damage, balanced speed\maneuvrability, cheap, black. Disguise as peasant, mount and go battle, enemy will think that you are peasant with staff.