Which computer should I buy? i3 12gb RAM or i5 4gm RAM. i5 is 40$ more. Both are HP all in one desktops.?

None. Building your own is much easier, cheaper, and you get to pick the parts you want! HP is a good computer company but building one is better. If you don't want to build one, I would suggest the i3 with 12GB of ram because 4GB of ram is bad for an i5. Best wishes! :)

Uh, this tells us next to nothing... but what it does seem is they're both not good deals.

You've got the first laptop where the manufacturer is trying to make it look good by putting in excess RAM.

And you've got another laptop that must be rather old if it only has 4 GB of RAM.

You need to compare the CPUs with benchmarks to tell which is better. Look up the model number of the CPUs then use a benchmark website like CPU World or Passmark to see which CPU gets the higher scores. That's how you tell which one is faster.

The i5 is a much better chip. Ram is easy to expand later as you discover whether or not you need it.

You didn't explain what the computer would be used for, so without that information, I'd opt for the i3 processor with 12GB of RAM. Take a good look at the reviews for upgrading any "All-in-One" computer. Some have limitations.

Go for the better chip - the i5. But, save some $$$ and expand your RAM, later!

How should we know? You didn't bother to tell us anything relevant. What do you need it for, why are you wanting an all in one?

What's the computer suppose to use for?

yes, i5

Neither one. All in ones' are crap!