Adding my 2 cents on this one as well, though it also aligns with @bjoern__koth and @abhinavbalooni.
The best solution is always the one that works for you. Only you know what your needs are.... now, if you have a set of websites that all do much the same thing (like in our case, we have 30 newspaper sites, and they are based on the same code base), and you need to report on them as a whole and as separate entities, than a single global suite with multiple virtual suites is probably a good idea... It's always easier to segment out sites than to try and add them together (especially if you have traffic that traverses between sites often, then your UVs will be de-duplicated within the global suite if configured correctly). As the others said, this is also very helpful for subdomains (tracking the domain as a single entity and splitting based on the sub-domains. (In my case, each of those 30 news sites have at least 4 sub-domains for related classifieds, obituaries, etc; and three of those sites have mobile apps - so my virtual suite configuration allows me to pull in many combinations of data from Core Site X, to Site Y plus all external). This also allows me to create a single report with dropdowns that allow people to choose the combination of sites, platforms and content to get the specifics of what they need... but again, this comes down to if this is something you want or need.
Now on the other hand, if you have a set of unrelated sites, it may not make sense to combine them into one... from a UV and cross site perspective it might be nice (and again this comes down to your needs), but if the tracking profiles are fundamentally different you will have to reserve dimensions and events that only pertain to some of the sites so that you don't have data from two completely different things in the same reserved components... some of the main "global" dimensions/metrics can be shared, but this could make your tracking design more difficult (but not impossible).. so if you feel this is something you want and can keep it straight, by all means proceed with that approach.
One other consideration you should be aware of is that each dimension has a "unique value per month" threshold (within Workspace), so the more different values you collect, the sooner you can potentially hit the "(Low Traffic)" bucket... however, the limit was raised earlier this year from 50,000 to 2,000,000 so this may not constitute a problem for you, but its a good idea to take into consideration when making your decision.
