Always ask yourself what are you comparing logically.

In ur example, you are comparing me and you.So the 2nd option is right.

But consider this: My house is bigger than you. : Doesnt make sense. It should be : My house is bigger than your's.

IT is not necessary that you can only compare only subjects or only nouns.This example is similar to an OG 12 SC question.It is one of the toughest comparison questions.

There were twice as many UFO sightings in 2001 as in 1950.

See I made a comparison between prepositions in 2001 and in 1950

It comparison being made is between the number sightings in 2001 and the number of sightings in 1950.

You can also say :

There were twice as many UFO sightings in 2001 as were in 1950.

But in some cases you have to repeat the verb because without it the comparison might become ambiguous.

A cheetah can catch a deer much faster than a tiger

The above is ambiguous because the sentence could have 2 meanings:

Cheetah can catch a tiger in less time than a cheetah can catch a deer.

or

Cheetah can catch a deer in less time than a tiger can

To clarify you use the verb

For you intended to say the former,you say:

A cheetah can catch a deer much faster than a tiger can.

If you intend to say the latter,you say:

A cheetah can catch a deer much faster than it can catch a tiger. [it is not ambiguous;it logically refers to cheetah]

In addition to all of the above, note that comparisons usually involve ellipsis, that is, omitting a part of the sentence which logically should be there, but is repeating what has already been said:

• Full: John runs a mile faster than Jack runs a mile.
  Ellipsis: John runs a mile faster than Jack.

• Full: There were twice as many UFO sightings in 2001 as there were UFO sightings in 1950.
  Ellipsis: There were twice as many UFO sightings in 2001 as there were in 1950.
  Ellipsis: There were twice as many UFO sightings in 2001 as in 1950.

Both formats are grammatically correct, but ellipsis is commonly used to make sentences shorter. So in the third option you are not quite comparing "in 2001" and "in 1950"; it's just a shortened version. You are comparing how many UFO sightings there were in 2001 to how many there were in 1950. However, in some cases, the items compared are not even partially similar, so ellipsis is not an option:

• Full: There were twice as many UFO sightings in 2001 as there were Yeti encounters in 1967.

rx_11 wrote:
1. eg. I have less money than the money of yours.

However, experts have pointed out that this sentense is wrong because it incorrectly compare "I" & "money".

Well, the following sentence would be correct:

I have fewer cars than the number of cars you have.

This is not comparing I with the number of cars.