We are capturing a personalized cart abandon URL for a cart abandon email and passing it into a field in Marketo. My question is do I populate it into a URL field or a String field? Is one better than another for a specific reason? I know when populating a link via a token, in order to have the reporting register the token as a link, we need to leave the protocol (http:// or https://) outside of the value in the token. Does capturing the URL in a URL field circumvent this? Do we need to leave off the protocol? Etc I'm just struggling with what the difference is between the URL field and a string andthe doc isn't very clear on that.

If you wish to store only urls in this custom field then I would suggest using URL datatype as with the URL datatype you may store the protocol and use the token for same without pre-appending the protocol like string field. Also the string field has the character limit of 255, this might be bottleneck for larger urls.