Another domain vs sub domain question

[Horizon]

Hi folks,

Another domain / sub domain query. Here's the back story (apologies - it's quite long!):

We run a successful French property/lifestyle/holidays website (FrenchEntree) and currently have a property database on a subfolder of this domain. Our host has really let us down in particular with the property database, so we're moving the property database to a high-end Tier IV datacentre with a different host (as part of a database redesign). With the move, we are left with two options - sub domain or separate domain. FrenchEntree has great long tail SEO and about 95% of the traffic to the database goes via FrenchEntree, or goes direct. The database has very little SEO presence as a standalone site, but accounts for the majorty of traffic (in terms of page impressions and time on site).

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My questions:

If I move the database to a separate domain:

• will FrenchEntree lose SEO value and domain authority because the traffic levels will inevitably decrease with the loss of the database? Does google pay much attention to traffic, or just site size?

• will FrenchEntree gain SEO value because the database has 1,000s of pages, and generally it is not particularly SEO friendly?

• will the database lose even more SEO presence (if it even has any!) because it is no longer associated with FrenchEntree?

• we imagine the new database will be much more SEO friendly as it has been built with present-day SEO knowledge in mind, but how costly/benefitial will it be to either site to have so many "external" links between the two sites? (the design and navigation will be the same on both sites, so there will be "external" links on every page because of the nav)

If I move the database to a sub domain:

• will FrenchEntree benefit from the traffic that the database brings if it is on a sub domain?

• will the database struggle to find its own feet with SEO being on a sub domain? I have done a lot of research and my general feeling is that sub domains rank very poorly in SERPs.

• is there any potential impact on FrenchEntree with the database moving from a sub folder to a sub domain?

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I appreciate that this is quite complex and thorough so will really appreciate responses. I may even through in a magazine subscription for the best answers!

Thanks very much Mozzers!

Matt