I’m still using Interworx v. 6.x. If I look at a Siteworx account, and go Domains -> DNS Records, then click the Edit link for an SPF record, I now see that I can select either version 2 or version 3 of SPF. It looks like all selecting SPFv3 does is change the “v” tag to “v=spf3” and doesn’t make any changes to other tags or offer new options in the UI.
I haven’t been able to find anything relevant about SPF v. 3 by Googling it. What, if any, are the reasons to select SPFv3 vs SPFv1?