As hard as it may be to believe, a surviving population of 1800+ is not small. Therefore the 1935 $25 notes are not considered rare. There are plenty of other Canadian notes (types and varieties) with much smaller numbers available to collectors.
We don't know how many of the estimated 1840 notes not accounted for by the Bank are in collector hands. Some notes have likely been destroyed (by fires, floods, eaten by dogs etc), while others have been lost and may never be found. Others are tucked away or "hidden", meaning they have yet to reach the collector market. What makes the 1935 $25 note valuable is its popularity. Pretty much every collector of Canadian currency (domestically AND internationally) has one or desires one. That fact alone pushes the value of this type note much higher than many rarer notes.
If your note is high grade, that's good. You are guaranteed a healthy sum of money if you ever choose to sell it. If it LOOKS really nice, you could get a lot more. But having said that, don't try to change your note by cleaning it, pressing it, trimming it, etc. The savvy buyers, who are the ones with the $$$, know what an altered note looks like. Buyers who suspect a note is tampered with will avoid it and it will sell for a much lower price. So don't tamper with your note and don't hire someone to do it either. Lots of people who monkey around with notes think they are doing a good job, but they really are not. If you have pictures of your note, I could give you a free assessment.