The old one is a nice filter, and works well, but the reason I am switching it out is because it's a bit too much flow for my angelfish and pleco. It's an Aquaclear 70 on a 29 gallon, so even on the lowest setting, the fish prefer the opposite side of the tank.
The only reason I have this filter is because I used to have a goldfish in that 29 gallon and, well, you know how that goes...😉
2.5G - 1 female betta: "Miss Cleo"
5.5G - 1 betta: Half-moon King "Cobalt"
10G (with 4G of water) 1 female betta "Grace"
29G - 1 gold marble angelfish "Bartholomew"
1 Male fancy guppy "Guplet"