What is the best way to place 3 destinations in 1 site or 3?

Question

Business Informatics

The company is engaged in 3 areas: Construction, metal structures, equipment rental. I can't figure out how to make the site better.
1st Option: Make 1 site with all 3 directions (with the same design for each direction).
2nd Option: Make the main website of the "Construction" direction and make 2 Landings "Metal structures" and "Rent of equipment pages" (Each site has its own design)
What is the best way to do it for promotion and for user convenience?
Maybe someone has a better option?

Answer 1

I'm not an expert, but you can make one site and three landing pages. Landing pages in different colors, but with common design elements, so that it can be seen that the owner is the same. And use recognizable fragments of the design of the main site.

Answer 2

make one site. and SEO to help you

Answer 3

Three separate sites + one main one, the task of which is to spread to the right directions (and to aggregate news from all sites, for example).
The main site (bringing to referral sites) is convenient to use in general contacts, give a link to partners. And all advertising companies, SEO are sharpened for the site of the direction.