For radius authenticated SSIDs, you need WPA2-aes or wpa1-tkip-CCKM. It depends on what the client supports.
For pre-shared key, any WPA should be decent enough for roaming speed.
If you're on WEP ... no comment.
If you covered the above point, check if it's not a coverage problem. If the 2 APs coverage zone are not overlapping there will be a hole where you don't have signal and logically will have packet drops.