I have one site by thematic...I have 6 thematics (guaranty departures, adventures travel, classic travel, landscape travel, ...) and so I have 6 websites (each website has 4 languages).
One of my objectives is to be as well as referenced on theses keywords (ex: guaranty departures bolivia, ...) if theses 6 websites are just wrapped inside a bigger one.
I hope that my question make sense..., thanks you by advance for helping.
I asked a similar question some time ago and the consensus there and in my own further research is to do 1 big site to gain the maximum benefits from backlinks. High quality links to multiple sites only benefit the site receiving the link but links into a single large site raise the profile of the whole thing.
It's more challenging to provide comprehensive navigation but the overall boost is worth the extra effort.
One big website is better. You can build a cohesive brand around it. Branding is good for all types of marketing.
Up until this year, Google had been giving a boost in the SERPs to sites that had an exact match domain (EMD). So if you were selling widgets and you owned widgets.com, you would rank well. Now, Google has taken away that advantage. So now, even launching on 10 EMDs is not a good strategy.
This especially true since all the examples you gave have a common "travel" theme. It would be hard if you were trying to build a big site that tried to merge your hobbies coin collecting, gardening, and rolex watches.
