On a serious note - WHICH Forrester model? If its the top of the line version with high HP, Turbo its definitely faster, quicker. Now assuming you're wanting something STURDY, RELIABLE and good to drive. This is what would be my arguments:
LOOKS: I like CX5 better as it gives same features for the same price point, however it looks better, substantially better both exterior and interior.
AWD: Although its generally thought having AWD ALWAYS (as in Subaru) is good, however CX-5 has a AWD system which is light years ahead in terms of technology in comparison to Subaru. It can give proper traction, speed, torque to individual wheels depending on need which it determines in milli-seconds. This greatly improves driving in icy/slippery conditions.
Engine: CX5 has the most advanced engine setup in the world today when comparing value cars. It has the highest ratio of compression among any car. What this boils down too in at a relatively low horse power it seems to get better performance equivalent to a higher horsepower car. Couple it with tremendous fuel economy benefits - both from this type of engine and intelligent AWD system ; in the long run there's lot of value.
Transmission: Subaru CVT is the best among all CVTs. However, inherently CVTs are bad. On the other hand CX-5 is above and beyond CVTs by re-engineering the standard transmission to such an extent that it behaves like a standard transmission but gives almost all the benefits of a CVT.
Finally: There are few issues with Forrester where there are forum thread running into pages. Whereas for CX-5, there's only 1 thread about few transmission failures - which is EXTREMELY rare occurrence.
Audio/Infotainment: CX5 Infotainment system is MUCH, MUCH better than Subaru's. But Subaru's Eyesight system is much matured than CX5.