Hi, Matt here and I can help you (former technical writer with a certificate and 21 years a webmaster).
I can create a comparison document in max. 2 days. Here are the main points of a spreadsheet (in Excel?):
1. Technical infrastructure: site platform, hosting, database, using cloud, site performance, responsive design.
2. Search engine optimization: number of pages (indexed in Google), SEO report - including on-site and off-site report, the age of a domain and a website, owners of domain, video SEO strength/issues.
3. Marketing view: landing pages, lead magnets, easy navigation, graphic design and branding, contact page, legal confirmance, guides/brochures/wizards, authority impression etc.
I believe there should be an easy to follow short Word document about each site (can be on Google Docs) and a spreadsheet comparing features with Yes/No and remarks.
Looking forward to your reply,
Matt