At higher quality/bitrates, the difference is much smaller and device support is universal for AVC and quite good for HEVC. Anything over 1.5GB for a single episode would probably only be farily similarly sized with AV1.

There is one large exception, but I don't know the current scene well enough to know if it matters: sources that are grainy. I have some DVD and blurays with high grain content and AV1 can work wonders with those thanks to the in-loop grain filter and synthesis -- we are talking half the size for a high-quality encode. If I were to encode them for AVC at any reasonable bitrate, I would probably run a grain-removal filter which is very finicky if you don't want to end up with something that is overly blurry.