Performance question.

Okay, so I love retro games... And I have made a few. I would like to create some for mobile, and I have a question. Performance wise, is it better to make a game with a resolution of 128x256 (just using a random number) and use sprites that are 16x16 and then use full screen scaling to make it fill up the whole screen... Or is it better to scale all of the artwork up to make it look like its only 16x16, when really its 64x64.. and use the resolution 512x1024? Basically, what is more taxing on the hardware/processor, larger art/sprites... or scaling? I have a game made that is a very small resolution and it runs a little jumpy from time to time, and thats what makes me ask.

Thanks!

Also, I have noticed that on the games where I scale the graphics up, I sometimes get weird artifacts. Like in this image, the art is all pixel, so the lines should be smooth, but if you look at the boxes below the players feet, they are clearly jagged. Also, the skull looks a bit strange, and so on. Is there a reason this happens? and a way to fix it?

I tried both pixel rounding, and integer scaling, no change to the weird jaggies on the art.

I think this may come from the scaling quality setting, does changing it correct this artefact problem? (Also low quality will perform better on larger displays, and for a pixelated game, the changes graphic wise should not be problematic, but I think I have encountered something like this in the past)