One of my brother has a 7 speed bike (21 speeds total) and it comes with entry level components. Compare to mines (9 speed, 27 speeds total). His bike feels heavier. The shifting isn't that great. Harder to pedal and his bike is much slower than mines. We went on a 20 mile ride one day and I offer him my bike to ride, in exchange for his for me to ride. I felt bad for him, because he couldn't keep up and is always resting. After exchanging, he was able to keep up. While riding his bike. I found myself switching to the largest chain ring a lot, to get more speed. With at least a 8 speed, you won't find yourself doing that as much.

Low entry bikes are usually heavier, less comfortable and operates like crap. Which won't feel that great on long rides.