Just thought I'd say my piece:
For a normal daily driver: Anything that's easy. Preferably the electronic manuals (Tiptronic; some companies call it) because I like controlling my gears for certain situations (overtaking, hills, etc. ec.), but working a clutch in stop-and-go traffic is a b***h. So little flicks of the gearshifter to shift gears is fine for me.
If I can't get ahold of an electronic sequential manual, I'll take a CVT. Seriously. If I can't get ahold of one of those (they're not very common), then I'll snag a manual (I really dislike fully automatics as the feeling of a gear being shifted outside of my control makes me feel unsafe; like I don't control the car. CVT does "shift" without my control, but... well, it's different.)
For a car intended for any performance purpose whatsoever: Manual. NO exceptions.
As far as the "automatic cars are faster than manual" or "manual are faster than auto" argument; both of the people on the first page are incorrect.
Simply due to the fact it is far too situational. Now, keeping dual clutch, multi plate, etc. etc. and all that funky transmission stuff in some cars today, and just focusing on a good ol' manual and a good ol' auto; the two are situational.
In the old days, manuals were superior to automatics in every way period. Except for perhaps convenience; but this is because older automatic transmissions had less gears than manuals; heck, even some fairly recent Toyota's have a four speed automatic transmission. The gear ratios are brilliant, which is why such limited transmission has gone so far; but four gears are less than five (no doubt.)
Back in the days of 2,3, and if you had a luxury car, 4 speed autos; manuals were being put out by the 3,4,5, and if you had a sports car, even 6 speed manuals. In terms of speed, versatility and economy; as long as the gearboxes were designed and ratioed well, the manual wins everytime. (unless you only have one leg or are really really really lazy)
Now, these days, the largest manual you'll find in a road car is 7-spd (in that new Porsche whatchamacallit), with 5 and 6 spd manuals being king. Meanwhile, automatics are being put out usually with over 6 automatic gears, heck, even sometimes up to 9 speeds!
In terms of mechanical efficiency; based on gear ratios alone, the automatic is more efficient as it has more gear ratios in which to use to keep the engine at a certain optimal RPM (whether it be for power, cruising, or whatever.)
Though that simply is not enough to look at. While on the surface, if you were at a dealership looking for the fastest ride and the dealership said "5 spd manual, or 7 spd auto?", you'd choose the auto, right? I mean hey, more gear ratios to play with means more efficient, right?
Not always.
What if the gear ratios are improperly specified? What if the 5 spd manual gears are wide-ratio and all the shift points seem to coincide with good shift points around a race track or on a drag strip, while the 7 spd has all messy ratios?
Think about it; lets say you have a bike; one has 5 spds and one has 7 spds. Lets say at 100 RPM (of your legs... thats a pretty reasonable speed), the 5 spd allows you to go 25 mph, while the 7 spd lets you go to 5000 mph.
Well holy damn s**t. I'd get that 7 spd in no time; no? I mean s**t. 5000 mph? I'd kill to go that fast!
Not so fast. Imagine just how god damn wide the gear ratios on the 7 spd would have to be in order to reach that speed. The torque on your legs would not be enough to even propel the bike 10 mph let alone 5000 mph; the gear ratios would be way too damn spread out (or perhaps the first 6 spds were reasonable, but the last spd was useless.) to be feasible.
So at the end of the day; the design of the gear ratios are kind over the number of spds. I could have a 58 spd gearbox, but if every speed was way under specced, overspecced, or in an odd place, it'd be useless. A simple 5 spd would kill my 58 spd gearbox.
Usually in a 5 spd; you have the first gear for starting acceleration, second gear for low speed cruising or continued acceleration, third gear for city cruising, fourth gear for highway acceleration or high speed city cruising and fifth gear for highway cruising. It looks like 5 spds would be all you need; all your needs are covered right there, no? Yep. They are.
So again; design > # every time.
But that's not all that goes into the difference between a manual and an auto. Lets looks at the key differences. One has a torque converter and flex plate while one has a flywheel and clutch.
Difference?
Clutch is a direct connection to the engine every single RPM the engine makes is an RPM transmitted to the ground if the clutch is engaged. Every single ft-lb of torque going through the clutch leaves mostly untouched coming out the clutch assembly. Its a direct connection. This is ideal in ALMOST every way when it comes to performance. It's also simpler and lighter to boot.
In some performance cases though, they are NOT ideal. Manual transmissions have the ability to wheel hop; the rapid grip and loss of grip. That is because the tires fight for grip, but the rigid and raw power of the engine is ripping the grip free; the sides alternate rapidly and you have serious wear and damage on your transmission parts (usually differential.)
Automatics on the other hand use torque converters. It is simply a case that contains very thick liquid that transmits the power of one rotating shaft with an impeller to another shaft with an impeller (one shaft being the engine shaft and the second one beign the output.) This has it's disadvantages because think about it; the medium is liquid. An RPM made could POTENTIALLY be lost in churning the liquid. A ft-lb (or more) of torque made from the engine could be lost through churning the liquid. Though this rarely happens once the torque converter is warmed up and is in proper operating conditions (most conditions), but the possibility is still there. They are also heavier and more complex.
They do have some benefits though; one benefit is the ability to NEVER be able to misshift or spend excessive time shifting. They also have a lesser chance of exhibiting wheel hop as if the tires have grip and want to keep hold their grip, they will slow the output impeller in the torque converter and some torque from the engine will be shed off into the TQ (torque converter) liquid, lessening the chance of wheel hop.
...
So basically; manual = automatic in general performance. It really depends on certain cases. Sometimes the auto is faster; sometimes the manual is faster. Sometimes no manual is availible. Sometimes no auto is availible. Sometimes only some hocus-pocus dual clutch, multi plate, flappy paddle, ecu, wizardry crap is the only option...
It depends...
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