Resing one video to match another?

[ChasVideo]

I am using AviUtl. I have one video with a logo that is 1920x1080 and flv format. I have another without the logo in 640x480 DX50 format. After I make my edits, I am planning on outputting the project as H.264. I will make a mask to display the lower resolution video through where the logo is.

What is the best way to resize the 640 video to 1080? I know it will not matter much. But I like to over-think quality. I could use the AviUtl resize and do it on the fly while re-coding. Or I could use some other program to re-code the 640 video to 1080. What will do the best quality resize?

Crud. Looks there is no way to edit the misspelling in my title

[s-mp]

NNEDI3_rpow2

[abolibibelot]

I mentioned Avisynth in this related thread, in case you were puzzled by the laconic reply above, it also refers to Avisynth. From what I could read, it is the best available filter for upscaling, which is what you need here. Others may be more suited for downscaling, although I don't remember the specifics.
In fact you could probably do the whole matching / resizing / overlaying with Avisynth, then use ffmpeg to encode the result directly from the AVS script. (The alternatives would be actually more complicated : either encoding each framerate converted and/or resized video with a lossless codec if you care about quality — which means huge intermediate files — then loading those files into AviUtl ; or creating “virtual” uncompressed files from the Avisynth script using AVFS, then loading those “virtual” files into AviUtl — this solution doesn't require extra storage space but is quite complicated to set up the first time, and can present reliability issues when the script becomes complex.)