Some quick comparisons specs;
Eheim 2262
Filter Flow Rate: 900 GPH
Filter Volume: 4.8 Gallons (18 liters)
Mechanical Surface Area: 122 sq/in (Roughly) (For coarse and small particle filtration)
Inlet / Outlet: 1" / 5/8"
Fluval Fx5
Filter Flow Rate: 600 GPH
Mechanical Surface Area: 294 sq/in (Roughly) (Coarse filtration ONLY)
Mechanical Surface Area: 28.26 sq/in (Small Particle and Biological Filtration ONLY)
Mechanical Volume: 369 cu/in (Roughly) (Coarse ONLY)
Biological Volume: 5.9 Liters (According to Hagen)
Outlet/Inlet: 1" / 1"
Eheim 2262 would be better in my opinion. Especially if you are going to run small partical filtration. The 2262 wont clog nearly as fast as the Fx5 in theory. Although the 2262 does have a higher output.
I do believe you will have more bio volume in the 2262 than the Fx5 evan after having 3" of mechanical filtration.