To compare the 3500 & 125:
The advantage of the 3500 over the 125:
- You get 2000 channels instead of 500.
- Systems are automatically sorted by Quick Key.
- Group quick keys, simpler to use than the BCT15X for example.
The advantage of the 125 over 3500:
- Bigger display
- Temporary lock-out.
- Only uses 2 AA batteries, not 3 as the 3500 does.
Annoying design flaw of the 125:
- A hare-brained bank & channel numbering system, so that bank 3 is channels 101 to 150, forcing you to constantly do mental arithmetic when you want something. (Any sensible designer would have given it 1000 channels, and bank 3 would be channels 300-399)