I'm going to copy-paste some things I wrote for another forum where someone asked the same question...
Pathfinder has several rules issues where it is inferior to 3.5e
1.) It didn't fix the things it set out to fix. The marketing things (during the beta) that said it fixes balance problems are flat out lies.
2.) Several of mundane's tricks got nerfed.
2a.) Let's start with the rogue. The Rogue can no longer sneak attack balancing enemies and full attack them. Rogue can no longer sneak attack with splash weapons, and thus get typed damage that isn't subject to damage reduction. Rogue can not sneak attack with ring of blinking. Ranged sneak attack builds are near impossible. Rogue cannot draw more than one alchemical item per round in any circumstance, even with quick draw, unlike 3.5e. Rogue is no longer mobile, due to the massive increase in tumble DC's, so he can't move around the battlefield to set up flanks. Further, the claim that 'PF rogue is better because fewer things are immune to sneak attack' is invalid because bypassing those sorts of immunities is fantastically easy in 3.5e, what with weapon crystals, cheap spells in wands, and several alternative class features. Plus, there are options that work against Fortification armor and effects in 3.5e, which don't work in Pathfinder. A conscientious Rogue in 3.5e is much, much, much more likely to get sneak attacks while fighting in 3.5e than in Pathfinder!
2b.) And on to Fighters. 3.5e's Improved Trip grants +4 to trip and lets you make a free attack after tripping. PF's: Improved Trip grants +2 to trip. A second feat (which you can't take until lv6 at the earliest) grants another +2 and lets you make an AoO after tripping... except that this replaces the AoO you'd get when they stand up. You can no longer trip fliers, which in 3e caused them to stall. So even though you get more feats as you level up, the feats themselves tend to be worse. The fighter chassis got slightly better, but none of the (say) charging or power attack feats that the fighter relied on for solid damage came through unscathed. Power attack got hideously nerfed. Grappling is no nowhere near as useful for grappling based meleeists to do (Grapple now takes a standard to use and a move action and a new check each subsequent round to "maintain" (failure = they're free) and is far less penalizing than before (can use 1H weapons, still in your own spaces, can threaten and attack others, no loss of dex to AC)). Bull rush got nerfed heavily -- it rush now requires BAB +6 and 3 feats just to make the movement provoke AoOs, something it did with NO feats in 3E, and the checks against CMB are MUCH harder to overcome than the equivalent in 3e. Pounce is extremely hard to get in Pathfinder, where you could get it with a single level 1 dip into barbarian in 3.5e. Pathfinder nerfed some great 3.5e feats, like Mage Slayer (now called disruptive) or Stand Still (now keys off enemy CMD).
2c.) Monks. Monks can no longer take improved natural attack, use natural attacks after their flurry, apply fast movement to speeds other than land speed, acquire something like improved trip or improved disarm through their class (which is the greater versions in pathfinder), and they cannot use flurry of blows with only a single weapon, like, oh, unarmed strike (!!!!), AND grapple was nerfed. Monk was already perhaps the weakest class, they made it even weaker for some reason?!?
2d.) A good chunk of melee-specific monsters are now stronger at melee. Lions, Tigers, things that interact with the new natural attack rules, where all primary natural attacks stay primary no matter how many secondary attacks they get, and that if you attack with a single natural weapon, you get 1.5x strength to damage and get to use the two handed weapon power attack ratio. This nerfs player character melee compared to things they will have to face. Unless you are a spellcaster, and get to thus interact with the natural weapon rules yourself (Summoner's Eidolon, Druid).
3.) Lots of the more powerful classes were buffed. Wizards no longer lose access to their prohibited schools. Divination is now a valid choice of prohibited school. Cleric gains free martial / exotic weapon proficiency with their deity's weapon. The new Witch class has an at will save or die at level 1 (slumber, with no HD limit), and has a fort save or die at level 10 (Ice Tomb). These hexes are once per target, but there is a level 1 feat that lets you try again if they save. Creators claim they don't like power creep, but they offer several power creep options for casters (teleportation option for classic conjuration school, robes of arcane heritage item, compsognathus familiar, their version of the persistent spell metamagic feat, the synthesist summoner option, the spell perfection feat, dazing spell, bouncing spell, reach spell, selective spell... spellcaster feats are very powerful, and they get MORE feats...). They nerfed a few spells -- mostly the polymorph line, and low level stuff like glitterdust, but there are still dozens
of save or lose and fight ending spells all over Pathfinder, and they didn't nerf the biggest problems with trouble spells
Basically... Its a new system to learn and they didn't fix the balance. They, in several profound ways, made the balance worse. At least in 3.5e, melee could learn to do useful tricks sometimes... So why waste time learning a new system?
If you want to play a 'like 3.5e but better', look into Trailblazer
or the writeup of how to run a D&D style game with Mutants and Masterminds
... or better yet, Legend
(this is my favorite of all the options).