Kinkers,
Yes, you are correct. Assuming both scales are the same type and quality, the 25 pounder will usually be more accurate. Most instruments are rated for accuracy (inaccuracy really) as a percentage of full scale. e.g. 5% of 25 is better than 5% of 50 lbs.
A second source of inaccuracy is the fineness of the readout. Murf's right that most digital scales have more than enough resolution to matter. It might matter with a spring scale though.
But save the bigger scale for stripers. You might not need it every time out but you'll be glad to have it when you need it!!!

Hope this helps.