Blitting a cached PNG will always be faster than CPU based drawing code and I think the app size tradeoff is worth it.
Reading your PNG from the disk in the first place will be slower than reading a compact vector, rendering it and caching.
Re-rendering from CPU can often be faster than GPU bus access times on PCs.
Anyways, it depends on what you're optimising for. I was just illustrating how vector can be much better than bitmap in many situations.
Got benchmarks for that?
Blitting a cached PNG will always be faster than CPU based drawing code and I think the app size tradeoff is worth it.