I've been playing Monster Hunter 4, and it is quite a fun game! I'm playing on the 3DS XL (not the new one) and it still plays excellently! Though if you use the bow, it'll be hard if you don't have the second joystick due to the aiming... Also, should say I'm still quite early in the game...
Anyways, I was happy to see they had the Insectcutters dual blades, until I saw they took away the Dragon element boost :/ They are one of my favorite weapons from MH3, and they nerfed out the Elemental attack from it!
However, they did keep the Ludroth Nail Sword 'n Shield, which are still good with a boosted Water Element! (As far as I can tell, there's a few monsters that didn't come back from MH3, Ludroth being one of them, though you can trade with the merchant for it's resources)
Resources for upgrades are a bit easier to come by, mainly because the Large monsters are a bit more abundant, but aren't too difficult to slay. (Not like the Gigginox was in MH3... such an annoying monster...luckily it didn't return) It also helps that you can mount the monsters now to do extra damage. The entire battle arrangement is improved, though it doesn't ruin MH3's fortunately!
Also, right from the beginning you can get quite a good amount of different resources as pickups at gathering spots/mining/etc.
One thing I do hate is that there is one Large monster that has a very unfair hit box against you... no matter where you are it can hit you with it's tail if you are around it (which, unless you are using a gunner/ranged item, you will be around it) and it will spam this move! Luckily it doesn't do any elemental effects on you (unlike the Rathian's poison tail). Also, I do hate the rate of Large monsters that appear in the exploration part... however it gets you used to fighting more than one at the same time! (Replaying my savefile on MH3, I can say it helps make things easier in that game, kicked a Qurupeco and Rathian's ass at the same time!)
Speaking of the exploration part... I have a love/hate with it. I do love how it constantly changes the layout and such, plus gives you awesome pickups at gathering points, however they do spam monsters and make the herb, blue mushroom and Honey pickups alot rarer... but if you find any boxes or crates (3 always appear at the starting area) you can get alot of Field Med's and rations (even Field Meds+) which helps...alot.
I will say, though, that breaks are alot harder to preform on the Large monsters. Usually, in MH3, it takes barely any effort to break the great Jaggi's crest, but in this game, it takes effort! or...I'm perhaps just not used to the improvements on the battle system...we'll see.
But yeah, the variety of monsters you can run across earlier on makes for getting better weapons and armor alot easier!
Also, returning to MH3 from MH4, the battles against Large monsters goes by alot easier! Random encounter Large monsters I used to be cautious around or run away from are just so much easier! I also rely more on the support characters (the cha-cha's) more now that I got used to the helpfulness of the palicos! (which you get the palico's from the start, atleast you can get them from DLC's first as well as getting one main leader one right away. You also can bring one to two with you, as well as have the others train whilst you are away in order to level them up!)
So, in my opinion, I really do like the new game! It brings more than it took away (bye-bye water battles, hello jump attacks and mounting) and helps you improve and get used to the battles without making it too difficult to progress, but instead maintains a level of difficulty that keeps you on your toes without having you rage-quit! You actually feel extremely satisfied when you beat the difficult battles!