A Layer 3 Etherchannel is basically like a point to point L3 link with the exception that it is a logical link composed of two or more redundant physical links.
A Layer 2 Etherchannel is also a logical link composed of two or more physical links in a redundant and load balancing configuration but you do not assign any ip addresses to this link. This link can be part of a single VLAN or it can be a trunk carrying multiple VLANs. If you need to trunk VLANs over the Etherchannel then i would say go with a Layer 2 etherchannel.
