Retina display vs old style display, why not use @2x files for both?

I'm currently developing an app for both 3.0 phones and the iPhone 4. My开发者_Python百科 designer made a high resolution and a low resolution version of the design. Our app is now 6 MB which I personally think is a lot, so I was wondering: why not only use the high resolution assets for all devices? What are the cons of this technique?

Thanks in advance Bart

One word: memory. The older phones have a lot less of it, and opening higher-resolution artwork uses more of it. By including both, you only load the high-resolution artwork into memory on the iPhone 4, which has more available.

Using the high quality assets for smaller devices may also cause blur and artifact issues. To prevent blur issues, downscaling is often done manually. Also, be sure to only include the PNG graphics within your project (don't include any AI or PSD files). Finally, try optimizing your PNG files to further reduce the size (see here).