This is the biggest step towards making a private server, its so big that I have it on a different thread! Okay, so here we go!!
WOTLK--
ArcEmu vs MaNGOS
ArcEmu has a LUA engine but slower development, and is a much less stable core. However, ArcEmu supports Windows based operating systems better, whereas MaNGOS is better on Linux. MaNGOS has cleaner C++ code but has many hack bombs waiting to go off. 3.3.5 MaNGOS can hardly support over 300 players on Windows operating systems
ArcEmu vs TrinityCore
TrinityCore is the stablest of most cores, on Windows if you have appropriate specs and internet it can hold up to 5k players. However, Trinity is essentially a better version of MaNGOS, but has about half the hack bombs MaNGOS has waiting to go off, aswell as WoWD. Trinity and MaNGOS only support C++ (Rumor has it that MaNGOS is implementing a PY engine). TrinityCore is the only core that anyone has Gunship working on.
TrinityCore vs MaNGOS
TrinityCore is in my opinion the way to go, however we are all different. MaNGOS is better if you have a very low budget and less knowledge of C++. Trinity is harder to code on, but better stability-wise.
TBC--
TrinityOne
Only supports C++, stopped working on the project before it was properly working. VERY buggy and unsupported.
ArcEmu
Supports C++ and LUA, unstable but great for fun servers.
MaNGOS One
Only supports C++, incredibly buggy but has ScriptDevOne and active development.
OregonCore
Only supports C++, is 80% MaNGOS One aswell as 20% TrinityOne. Dead project but atleast 80% of TBC is working as intended.
SkyFireOne
VERY buggy, essentially OregonCore but has messed a bunch of crap up with hacks, etc. 100% Unsuggested by me and my emulation nerd friends.
Vanilla--
MaNGOS Zero
C++ Based, only actively supported 1.12.1 core, ScriptDevZero but needs real developers. 1/4-1/5 of spells are buggy as are ranged attacks and melee (Melee is very buggy).
MANY hackbombs in Raids *Classic example is Zul'Gurub, atleast 3 of the bosses have VERY serious hackbombs ready to explode. Can be perfected with devs.
TrinityZero
C++ based, stopped development after about a year. No longer supported but works a decent amount. About 1/3 of spells are bugged, but with real devs is more stable than MaNGOS Zero.
MaNGOS Platinum
C++ based, stopped development in 2008. Dusty and very buggy, picture the system banning you for entering westfall. Hardly works and its horrible. DO NOT use MaNGOS Platinum.
Operating Systems and specs.
Linux: TrinityCore is best supportive of Linux aswell as MaNGOS. Linux specs should have atleast 2GB Of RAM to run properly with 100+ players. Linux is much more stable and only requires checkups once a day.
Wandows (AKA Windows): ArcEmu THRIVES on Wandows, however eats MUCH more RAM. ArcEmu is very unstable but can be VERY well supported via Wandows with atleast 8GB RAM.
RAM requirements and why
In ArcEmu, each player eats about 0.1 MB of RAM, whereas Trinity and MaNGOS estimate around 0.05 per player. Trinity requires less RAM than MaNGOS and ArcEmu because ArcEmu takes about 800Mb to run by default, MaNGOS is about 600 and Trinity is 400 with both auth and world.
Speed:
To make a server with over 300 players per se, you'll need atleast 100MB up and down for download and 75 upload. Each player eats 0.075 MB, which is around 75KB. On average a casting/moving player takes about 120KB.
Funserver:
ArcEmu, hands down. ArcEmu is 100000x more customiseable opposed to that of Trinity and MaNGOS.
Blizzlike PvE and PvP: TrinityCore. More stable, easier to fix with less bugs.
Sorry MaNGOS, but you are the one voted off tonight.
Thanks for reading, hope I helped, best regards
--Turtleswin.
Need help deciding? Skype request iamaturtlehehe for more info or you can contact me via PM! Best of luck!