So I am bored and put together a summary of the current game state.
-Inner Sphere Quirks-
Inner Sphere Mechs got buffed via Quirks. Some are general quirks, like speed and agility bonuses, some are general weapon class quirks like Energy, Ballistic, and Missile, and some are weapon specific like AC/20, SRM4, Large Laser, etc. These Quirks have given many IS mechs new life, and also enabled them to equal or even outperform Clan Mechs.
These quirks can be viewed here: http://snafets.de/mwo/quirks.htm
My IS Mech "power" rankings:
IS Tier 1: Firestarters, Raven Huginn, Wolverine 6K, Dragon 1N, Stalker 4N, Banshee 3E, King Crab 000.
IS Tier 2: Wolverine 6R, Thunderbolt 9S & 5SS, Victor Dragon Slayer, Atlas D-DC
IS Tier 3: Raven 3L, Jenners, Griffins, Shadow Hawks, Cataphracts
The extreme majority of Clan Mechs are available for C-Bills. They are expensive, but well worth it. Their "high" cost isn't high when you consider that they come automatically with Double Heat Sinks, Endo Steel, Ferro Fibrous, and a Clan XL engine that doesn't destroy your mech from a single side torso loss. Almost all of the Clan Mechs are strong, however some are so strong they are the unquestioned kings.
My Clan Mech "power" rankings:
God Tier: Stormcrow, Hellbringer, Timber Wolf, Dire Wolf.
Clan Tier 1: Nova, Summoner, Warhawk.
Clan Tier 2: Adder.
Clan Tier 3: Mist Lynx, Kit Fox, Ice Ferret.
Clan Tier 4: Gladiator.
Wall of text here. Easier to describe in Teamspeak/etc.
If you have any questions, let me know. A lot has changed in the game from August 2014 to now.