How much more power does a 10 amp Dewalt drill have compared to a Ryobi 12-Volt drill?

You don't know electricity.

Electricity running through a wire " is like water running through a gulley.   You have trickle of water or a RIVER of water.  That is "current" measured in Amps.  I am pretty sure you can find it on the internet in an animated form(cartoons) to explain it.  So, it is boring for me to type what is already depicted in an animation somewhere.

.  It also explains voltage too in animations

. It also explains the difference between AC & DC power(cord vs battery)

. it may also explain the difference gearing has 

For Ryobi is a geared SCREW GUN on 12volt battery

The DeWalt is a 1/2" I am guessing corded drill120volt with a half inch drill bit meant for some serious drilling.  It can screw but those screw are in in an instant.

Ryobi max turning speed(RotationsPerMinute) is about 900 with a fresh battery. 

DeWalt's RPM is probably closer to 6000 so it does not go slow at all.  It does go slower with the variable speed trigger but going slow means it heats up and it has a fan inside it that rotates with the motor to keep it cool so you do not say screw in 1000  1 1/4" screws with this drill because you will overheat the motor. and burn it out.   You can't screw at high speed because you chance to come out of the screw itself ruining the screw.

The 12 volt screw drill is too slow to drill into concrete because that is a hard material so it takes a long time.  So does drilling in steel.  Battery will be dead 6 times before you get through 1/4 in plate steel.

They are both necessary.  Dewalt also makes a battery powered drill  16Volt so only a 16 volt charger charges it and only 16 Volt batteries from Dewalt fit Dewalt.

Ryobi fits Ryobi.  Manufacturers already figured out how to screw us.

All corded drills fit 120 Volt outlets. no Mickey Mouse there.

I don’t know the maths but as a rule of thumb, the more volts on a cordless tool, the better it will perform.

10 or 12v is a bit feeble, 18 is the minimum for a useful tool, although upto 56v is available as far as I know.

That’s still way short of the 240v of a mains drill. I have both, the cordless for thin wood and plaster board walks and the corded for thick wood and solid walls.

You cannot compare amps and volts any more than you can compare rivers and lakes. One is flow, the other is potential.

To compare POWER, you would need to either know amps and volts of both units or the torque at specified RPM, or the horsepower. There are numerous other tradeoffs between battery and cord-powered units, such as convenience when not near a power receptacle and the unlimited duration of use for cord-powered units.

They can weigh about the same.  I have several of each type. The Dewalt corded is useful in the shop or garage. The Dewalt battery is useful for short jobs away from the house or on the roof, where there aren't any power receptacles handy.  You still need to charge the batteries, and they eventually stop holding much of a charge.

If you already have  decent air compressor, there are pneumatic drilling and cutting alternatives (and nailing, sanding, etc), but you have to run an air hose to each tool.  The tool is then limited only by the compressed air supply (cfm and pressure).

Electric drills will always have more power than battery drills because they are being fed with a 20 amp circuit.

1 Volt is 10,000 amps so keep away from those volt drills 

the cheapest corded drill you can buy will always outperform the most expensive cordless drill...and in my opinion the ryobi is the worst you can buy 

easy 12 volt has 150 watts at the most and 10 amps have 1,100 watts of power .  Or a 12 volt has 1/10th of a horse power compare to 1and 1/2 horse power from a dewalt .

No 12V drill has any balls. There is no direct conversion from volts to amps. The DeWalt will twist your arm off if you let it.

The corded one has more power but you need to plug it in.  That Ryobi will handle light jobs but you have the convienence of taking it anywhere.  I use the 18 volt Ryobi for all projects around the house, even drilling into concrete and stone for anchor posts.

Edit. I fixed my typos. I was embarrassed. 

I think you mean 120 volt and it should say how many amps on whatever site your looking at. The higher the amperage the more power it has.The problem with battery operated is the batteries don't last very long before they won't hold a charge and they are expensive to replace.If you are considering a new drill go with corded.