Different subdomains v. subdirectories?

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Hi Moz community!

I am working with a team to launch an eCommerce project that is becoming increasingly complex.

The client has three major brands that are owned by a fourth parent company that they would like to bring together for the first time. We have done a ton of user research and have found that there is a good deal of overlap with two of the brands; the third is very distinct and the parent company is virtually unknown in America.

Because of this, we have designed different feels for each brand while making them significantly more coherent. We have also done our homework re: keyword and market research. Our goals are 1) unify and improve their brand identity, 2) create a supreme eCommerce user experience, 3) have smart SEO.

So here is my question: should the URL structure best be:

EX 1: brand1.parentco.com , brand1.parentco.com/products , brand1.paretnco.com/products/specific-product etc...

EX 2: parentco.com/brand1 , parentco.com/brand1/products , parentco.com/brand1/product

EX 3: parentco.com/brand1-products , parentco.com/brand1-products/specific-product

EX 4: brand1.com , brand2.com , brand3.com , parentco.com

Would it be best to have the brands on their own subdomain or subdirectory?

Does it make it looks like the brands aren't significant enough if they are on a subdirectory to humans and/or bots?

Are there problems with sharing cart information across subdomains?

Currently, between the three brands and the parent company there are about 8 sites that are basically copies of one another. Their domain authority is between 40-70 and 5 of the 8 sites have a significant amount of natural, high quality links. These current sites are basically like EX 4 above and are totally disconnected to one another. Regardless of the structure we chose we are going to redirect everything to keep as much of the current assets as possible.

Any insights or information would be so appreciated!

[William.Lau]

That is a lot of different variations. I suggest combining the similar ones and keeping the others on different domains.

Like brand1, brand2, brand3.

In my opinion, if you already have different domains and have significant links, that will only benefit you. Combining them would not do too much good and it might cause clutter.

Having multiple powerful and authoritative domains can be really beneficial.

Just my 2 cents.

[Adpearance]

Thanks! I suppose we have options. I am leaning towards going with EX 1 just for consistency's sake to keep all the brands together.

Thanks again!