Which One Is More Valuable?

Value depends on many things serial number is just one component.

I think it depends on the exact denomination and series. Since not all issues were printed to full capacity, solid 8's are often considered more challenging than solid 1's. At least that's what I read.

If you go by Canadian (Charlton GPM #31) catalogue serial #1 is typically much higher in BV (Book Value) than the Solid Radars (except for 1935/37 (P-38 to P-57) since so few solids have ever been sold in the first 2 BOC series). But I feel the BV is rather conservative for Devil Faces series since they seem to have a fanbase all of their own so FMV (Fair Market Value/what collectors will pay) may go well beyond. Charlton puts solid radars at $2100 for the $1 to $2900 for the $100 (P-66 to P-72). For #1 notes data begins with the 1937 Gordon-Towers or Coyne-Towers signatures $1 (P-58c,d,e does not clarify which) fetched $22,500 (but not sure when this sale was). Charts get a bit more consistent for Devil's Face Low # banknotes (P-66 to P-72) which are around $3600 (but these figures seem low). The demand for #1 notes & solids seems to merge for the more recent series but typically #1 go for more.

Fancy serial numbers are just a small part of notaphily. There's so so much more that collectors look for when collecting. The history and artistry are what fascinate me. As far as which serial numbers are more popular or valuable will become apparent once you've been collecting a while.