When developing, what is the way to achieve the best performance and the best quality?

To set PowerDraw high (for example 1024x786) and if a user wants a lower resolution, set my forms size to 640x480?
Or should I rather put my Powerdraw to 640x480, and once they want a higher resolution, I put my forms size to 1280x1024?

So, what do I use for best PERFORMANCE? And what do I use for best QUALITY? High PowerDraw resolution or a low PowerDraw resolution? And then I size my forms..

(sorry for the unclear question; I don't exactly know how to ask/explain it)

Thanks in Advance.