Looking at which mediums I don't already have quite a few of I have the three choices above. Bearing in mind the latest energy draw info (version 3) I was looking for some advice on which of those to get as there is the -20% mastery pack sale on. (I'm separately picking up the Catapults and Griffins)
Cicada - Very niche mechs in my opinion as they are basically playing like some kind of heavy light mechs. The three mechs included in the pack probably are the best ones - 3M with ECM + UAC5 + MLas; 2A can be played right out of the box, and the same is more or less true for the X5 as well. As a bonus, all 3 of them are bringing big XL engines of various sizes. Hunchback - I like the HBKs, but both the Hero and the Champion aren't truly great mechs. GI needs it's original Gauss CD as far as I am concerned, and the 4P - as unique as it is with it's capability to boat MLas (or SPLas if you like that) - very much is a kind of one-trick pony. The 4SP is purly awesome, though, especially when fitted for brawling. About your bang-for-your-buck, only the GI comes with an XL engine, and it's a rather small one. Centurion - YLW was the first hero mech ever released, and by looking at the hardoints alone it's long been surpassed by the power creep of the more recent releases - see the AC20 capable Enforcer for example. It's still very funny to run around in a 9x.x kp/h medium with a BFG and some lasers for backup, though, and it's quirks pretty decent as well. The champion's loadout is pretty dated (AC 10 + 2 MLas) and a bit similar to the D. The latter at least got a heavily quirked LB10-X currently (I hate those in MWO, but each to his own) and comes with a very nice XL300 (which probably goes right into your YLW in the beginning).
If you're interested in the hunchbacks, I'd have to push for the IIC version. They are too much fun. But as far as mastery packs, I think it kinda boils down to whether you'd prefer slight favor on AC's (Centurion) or Lasers (Cicada). Granted, I've only played like 3 matches with Cents in general. I'm personally not a fan of the Cicada-3M UAC5 build, as I find by the time you get enough ammo, ECM, and a couple back up lasers, its too slow for my taste. I do enjoy my 3 Cicadas, but really found I didn't do well unless I had them all with various combinations of Lasers, or a PPC or two on my 3F(Loyalty).
Aylek probably already said it all, yet here's my view anyway: Hunchbacks for versatility. They have a lot of variants with a lot of different hardpoints and nice quirks, which you can get in addition to the mastery pack. I am a big fan of the hunchbacks for their functional look which was also the reason I got the Founder's 4G instead of AS7-D Mount a lot of weapons high, wreck face. The 4SP is a crazy tanky brawler with all the structure quirks and lack of a profound hunch, much like the BLR-2C compared to the others, and the 4P has been a favourite laserboat of mine for a long time. The Grid Iron isn't rally anything special about a hero mech though to be honest, but it can do the BFG and some hybrid builds, so you can tweak a lot to find your right spot. Currently owned: 4G, 4J, 4P, 4SP variants (as horsemen of the apocalypse) Centurions for brawling fun. While the shoulder of the Hunchback is easy to hit, the Centurions are a much tougher beast. Also, centurions have hardpoints of every kind, which each hunchback variant is specialised into a certain role. The left arm can be used very effectively to shield incoming LRMs or brawling pain. The CN9-A(C) is as far as I know the awesome zombie build that I always find a great joy to play (though my variation uses a leftover engine and more ammo for the SRM6+A). YLW is a bit outdated by powercreep, the biggest problem is an arm mounted AC20 that can be shot off pretty easily if your left side is gone. For the rest it's still a fun mech. The CN9-D is just not my cup of tea. it has high speed and insane LBX quirks, making it more of a light hunter, especially if you add some streak srms. Light Hunters haven't been around since 2014 though... Currently owned: A, AH, D Cicadas for if you like playing lights. They're really just glorified lights and punished by putting them at the lowest medium mech wt class. Though, the 3M is a pretty interesting ECM mech with the ERPPC+AC sniper build, the 2A is a bigger JR7-F/any laser hardpoints light mech (thus, very effective) and the X5 no longer has the stupid 2 tube launchers limit, so can wreck face with double SRM6s, as the only Cicada with missile hardpoints. Pretty diverse builds but not particularly representing medium mechs. Currently owned: X5 (bought it waaaaaaayyy back in the day, saving up for 3M/2A next)
Much appreciated advice. I decided to pass on the Hunchback pack as I have the Hunchback IIC's and I'm not convinced by the Grid Iron, I'll just pick up the HBK's I want normally. Went for the Centurion as I hate meeting them in most of my mediums.... and the Cicada as I do like fast mediums/free XL's.