The 901486-06 ROM is only for NTSC-M systems with 14318181/14 Hz clock frequency and a 6560 video chip.
The 901486-07 ROM is only for PAL-B systems with 17734472/16 Hz clock frequency and a 6561 video chip.

"<" = 901486-06
">" = 901486-07

First, there is a difference at $e475. It must be a version number or
something.

< e470: c6 58 4c 74 c4 41 20 33 c5 4c 77 c6 ff ff ff ff : .XLt.A 3.Lw.....
---
> e470: c6 58 4c 74 c4 e8 20 33 c5 4c 77 c6 ff ff ff ff : .XLt.. 3.Lw.....

Then there is the video chip initialization table, which gets copied
from $ede4 to $9000. The horizontal and vertical screen origin
coordinates differ.

< ede0: ff ff ff ff 05 19 16 2e 00 c0 00 00 00 00 00 00 : ................
---
> ede0: ff ff ff ff 0c 26 16 2e 00 c0 00 00 00 00 00 00 : .....&..........

60 Hz VIA timer ($4289+2=17035 on R6, $4826+2=18472 on R7):

< fe30: ef a9 82 8d 1e 91 20 8d ef a9 c0 8d 2e 91 a9 89 : ...... .........
< fe40: 8d 24 91 a9 42 8d 25 91 60 85 b7 86 bb 84 bc 60 : .$..B.%.`......`
---
> fe30: ef a9 82 8d 1e 91 20 8d ef a9 c0 8d 2e 91 a9 26 : ...... ........&
> fe40: 8d 24 91 a9 48 8d 25 91 60 85 b7 86 bb 84 bc 60 : .$..H.%.`......`

Table of RS-232 timing constants:

< ff50: 91 ae 98 02 86 a8 68 a8 68 aa 68 40 92 27 40 1a : ......h.h.h@.'@.
< ff60: c6 11 74 0e ee 0c 45 06 f1 02 46 01 b8 00 71 00 : ..t...E...F...q.
< ff70: 2a 00 48 8a 48 98 48 ba bd 04 01 29 10 f0 03 6c : *.H.H.H....)...l
---
> ff50: 91 ae 98 02 86 a8 68 a8 68 aa 68 40 e6 2a 78 1c : ......h.h.h@.*x.
> ff60: 49 13 b1 0f 0a 0e d3 06 38 03 6a 01 d0 00 83 00 : I.......8.j.....
> ff70: 36 00 48 8a 48 98 48 ba bd 04 01 29 10 f0 03 6c : 6.H.H.H....)...l