For 3 years, it was the weight of the lappy rather than the screen real estate that was an issue. For the first 2 years, I had a 15-inch weighing in at 6.3lbs. That may not sound like a lot but together with books, recharger and other junk it really felt like boot camp 3-4 days a week. For the final year, switched to a 14-inch at 5.5 lbs, which doesn't sound like that much of a drop, but I could really tell the difference. Very happy with 0.8 less pounds to carry!
Both machines are good workhouses, having survived many a bump, jostle and even drop.
Excel and Powerpoint will be fine on a 14-inch. What, you got bad eyes or something? Just make sure that the brightness of the screen is high enough for you. Mine is somewhat muted. I've already maxed any controls to bump it up, so my next purchase I'll look for more brightness.