Check the filesize is the other system is double the size. That is the answer. For V3 the resize will use 10% compression rate while in 2.X is 25%. You shouldn't really bother at all in this. Really.
All right.
Please tell me where you can improve or even remove the compression ratio.
I want to get the same great quality in the preview, as in the original.
Size is not important for me.
Thanks in advance!