This thread is aimed mostly at the players who still hesitate and can't choose between a rogue and a feral druid. For years there wasn't a really good reason to choose a feral over a rogue, but with the latest patch finally the balance has been achieved.
I'll try to compare rogues and ferals by several key factors.
1. Stealth - 50/50
Since 4.0.1 both rogues and ferals have the improved stealth (opposed to balance and resto druids). Moreover, talents and racials that improved stealth or stealth detection are gone, meaning that rogue and feral have now the same chance of catching each other first.
Update: There are some rumors that ferals have better stealth, though it's not official.
2. Healing debuff - 50/50
The "mortal strike" debuff is now only 10%. Rogue provides it by reducing healing by 10%, feral provides it by increasing mana cost of spells by 10% (which will matter soon). The interesting thing here is that the feral ability stacks with other mortal strike effects - meaning you can have healing reduced by 10% and mana cost increased by 10% at the same time, giving an overall 20% healing effectiveness reduction over a long period of time.
3. Interrupt - 50/50
Ferals now have an interrupt, just like rogue - for 5sec, 10 sec CD. The feral one is even somewhat better since it can be used from 13yards, as opposed to 5. However, the feral one can't have an "improved version", i.e. silence.
4. Damage 50/50
Overall the damage of both classes is equal in a PVP setting. Feral has an advantage over heavily armored enemies and rogue over lightly armored ones.
5. Control from stealth - rogue
Rogues still dominate in this area. They have Sap and Garrote silence, which ferals don't have.
6. Control from out of stealth - feral
Rogues have blind (long CD) and gouge (short CD), but both break on damage. Ferals have cyclone, which always works, and becomes instant and free of mana every time you apply a 5CP finishing move. Ferals also have entangling roots, which can be made instant cast either with the glyph, or with a 5CP finisher. Ferals have nature's grasp, which applies roots up to 3 times upon being hit.
7. Stunlocks - 50/50
Feral's stuns don't share diminishing returns, rogue's - do. Feral's stunlock lasts 9sec, rogue's - 7sec. But during a stunlock the rogue does much more damage than a feral, so normally a feral never stunlocks, but rather uses rip.
8. Silences - rogue
Rogues have garrote and improved kick, ferals don't have any silences.
9. Self healing - feral
This one is even or in a slight advantage for the feral. Rogues have a hot and ferals - an instant heal after each finishing move. The advantage goes to feral, because rogues have to sacrifice their finishing move for the heal, and ferals - don't. However, ferals must go caster form for the heal anyway and need to spend a GCD to shift to feral again.
10. Restealth - rogue
Rogues have vanish and cloak of shadows, ferals have none. Still rogue domination in this area, as it should be.
11. Offensive CDs - 50/50
Ferals have Tiger's fury - 15% damage increase for 6sec (30sec CD) and Berserk (adrenaline rush on 3min CD). Rogues have several depending on the spec, but in my opinion they even out in the end.
12. Defensive CDs - 50/50
Ferals have Survival Instincts (50% damage reduction on 3min CD) and shifting to bear form, which in turn has Frenzied regeneration (last stand effect, and heal to 30% effect). However, shifting to bear greatly diminishes the effectiveness of your bleeds, because the bleed mastery works only in cat form.
Rogues have Cloak of shadows, Evasion, Combat readiness (soon to come) and Smoke bomb (soon to come). Subtlety rogues have Cheat death as well.
13. Mobility - feral
Rogues have their sprint on a 1min CD, ferals - 2.4min CD. However ferals have Travel form and 4Piece PVP Set bonus for even greater speed outdoors.
14. Survival against stuns/fears/polymorphs - feral
Edit: added some updates here
Rogues have nothing to counter stuns, ferals have Barkskin, which reduces damage by 20% and chance to be crit by 25% (with the glyph) and can be used while stunned. Ferals break fears with Berserk, rogues can't break fears, but can prevent them with Cloak of shadows. Ferals can't be polymorphed while in a cat/bear form, but if you were polymorphed while human, you can no longer shift to break it.
15. Survival against roots/slows - feral
Rogues have vanish and improved sprint, ferals - shapeshifting. The ferals however can do it no matter how many times so they have the advantage here.
16. Combo points generation - rogue
Rogues have several abilities to generate combo points and their openers award more combo points. Ferals only have 2CPs at once on a crit.
17. Energy regeneration - rogue
Rogues have several talents that increase energy regeneration rate (different per spec) or award energy on finishing moves, etc... Ferals have a burst energy regen tool on a 30sec CD - tiger's fury. In the long run however rogues regenerate more energy.
Both rogues and ferals receive a refund of 80% of the energy of a finishing move if it misses/is blocked/dodged/parried.
18. Slowing the enemy - rogue
Rogues have the advantage with Crippling poison (70%) against Infected wounds (50%), the second however is physical to make up to an extent. Both are reapplied by the normal attack cycle and don't require wasting energy to do so.
19. Catching the enemy - feral
Ferals have feral charge (30sec CD), subtlety rogues - Shadowstep (20sec CD). If ferals play in bear form, its CD is 15sec only. In the end it evens up. However non-subtlety rogues have no analogue to that which is a big problem in pvp.
20. Switching targets - rogue
Rogues will soon have Redirect, making switching easier.
21. Disarms - rogue
Forgot an important one
Rogues can disarm.
Update: Ferals are affected by disarms, but slightly, since only some of their attacks are based off weapon damage. The most important ones (bleeds) remain the same. No feral attack becomes unusable after being disarmed.
*Additional utility - as a hybrid class, druids provide additional utility over rogues. Rogues have also some unique niches, but overall feral ones are more useful.
Ferals have tranquility and combat res.
Rogues have Detect traps and Disarm trap.
It's hard to tell yet which will be more useful in cata - my guess is rogue for arenas, feral for rated BGs, but one thing is for sure - feral druids are more viable and closer to rogues than ever before. Each have their own advantages and weaknesses, but in the end one thing is for sure - if you always wanted to play a feral druid, but never did due to any reason, now is the good time to try it