Are i7 laptops better than i3 & i5 laptops ?                                                                          Generally yes, but it depends on specifically which i3, i5 and i7 you're comparing.

Let me give you an example of how confusing things can be:

Right now Intel sells the dual core i7 8500Y which is intended for ultrathin laptops. They also sell the i3 8100H which is a quad core processor that is significantly more powerful than the i7 8500Y and has much more powerful integrated graphics.

The i3 8100H is also cheaper than the i7 8500Y so a laptop with it will also be cheaper. So why is this? Well.. let me explain:

When looking at an Intel processor you can not look just at the letter and number i3, i5, i7 and i9, you also have to look at the rest of the with its numbers and letters.

Here's how a model name for an Intel Core processor is built up. The most important things to look at here are the generation indicator and the product line suffix.

In the case of the i3 8100H the generation indicator is 8, and the same for the i7 8500Y which means they're part of Intel's 8th generation of processors.

Now let's look at the product line suffix of which can include either none, one or in some cases two letters. There are also cases where there's one letter and one number. Here are the most common suffixes for Intel laptop processors.

As can see “H” means that the processor has high performance graphics. Sometimes they throw on the “H” to just indicate that the processor pulls more power than let's say a “U” series processor. The HQ appears sporadically and some quad core processors don't have the “Q” for some reason only Intel knows.

But as you can see the Y series of which the i7 8500Y belongs is the “Extremely low power” series of mobile processors. This series has up until and including the 8th Gen been extremely power efficient dual cores with hyperthreading that can use as little as 5W of power. This means significantly better battery life and it means it runs so cold that you can run the processor without a fan in an ultrathin chassis. 10th gen will for the first time bring some 4 core CPUs to the Y series.

The U series up until 7th Gen were also two cores max, but now they now go up to 4 cores, and next year there's even talk of a 6 core. The TDP of the U series is usually 15W, so a little bit more than the Y series, but still fairly power efficient.

The i3 8100H is a more “beefy” processor with a 45W TDP. This means that it's meant for more powerful, but thicker laptops. The H, and especially HK suffix i3, i5, i7 and i9 processors are usually found in bigger and thicker workstation laptops or gaming laptops.

Hope this helps. Intel's naming schemes can be extremely confusing so it's understandable that it's not easy to pick the right laptop sometimes. In general a higher number means better, but not always.

Good luck.