differences between simulators servers ?

hello
i need informations about :
- differences between servers classes (4,5...)
- differences between mainland / real estate
i cant find these infos in the site or the wiki.

we can ear everything "in world", so, do you know where to find "real" info about this ?

1)
http://blog.secondlife.com/2006/10/16/looking-forward-to-class-5/
...

So, here’s what’s different under the hood: we’ve been all-AMD for years, but are moving from the Opteron 270 to the Intel Xeon 5148 - a low-power version of Intel’s new Core 2 Duo based server CPUs. This gives us better performance for fewer watts, while supporting our standard 64-bit OS image. We’ve also doubled the RAM per machine from 2GB to 4GB and moved to a faster SATA disk, which usually won’t make much of a difference, but should reduce the stalls sometimes seen by heavy regions during autosaves. Finally, there are fewer, bigger system fans, and power supply efficiency goes from 67% to 84%; power usage while running the sim process is about 175 watts, vs. 230 for a Class 4.

2) I assume you mean mainland vs estate (also referred to as private sim/islands)
Mainland is owned by Linden Lab for someone to own mainland property you have to be a premium member. Mainland property do not have any restrictions on it's use.
Estates are leased by a private party from Linden Lab. You pay your fees to the estate owner and you are subject to any and all restrictions of the estate owner.

One "real world" difference between class 4 and 5 servers is that class 5 servers can host about 2-2.5x the number of scrips of a class 4 in my own experience. Other than that nothing noticable. (Though that alone is nothing to sneeze at)

Also, class 5 servers cost $295 a month in tier to LL and Class 4 is (for now) $195 (Yes even if transferrred)

If you are looking to rent, land in class 4 servers or the mainland is probably cheaper than on a class 5.

If you are planning on owning a sim, on the mainland you are restricted in several ways, little land sculpting ability, mostly no privacy at all. If you buy your own sim then you have 100% privacy and access control and COMPLETE control over the land shaping, land textures, time of day etc.

thank you for attention,

about server class :
you speak about hardware, this is fine that these are bigger machines, but i need infos about "inworld" abilities.
in the second post i can see "run 2-2.5 more scripts", ok
someone told me that class 5 can handle 100 avatars... but i have never seen more than 50 without beein unable to move, so was it a class 4 one ?
is there a list with inworld difference instead of hardware ?
how to recognize if a sim is 4 or 5 ?

about mainland :
mainland and private sims can either be class 5 or 4 too ? or only privates ones are class 5 ?

the most difference i can see in your posts is that mainland is restricted about sim modeling (to correspond with the neighbours ones i presume) and the privacy is lost.