It is a huge difference..... I run 50/34 with a 11/25 cassette and I almost never shift to the 34T ring. We have only a couple big hills here, and I dropped to the 34T ring but did not need to get up to the 25T cog. For my style of riding and the terrain, I could ride 50/25 exclusively, but it's nice to have that cushion if needed.

For what it's worth, I'm 51........