Disclaimer: I don't have actual experience with these rods so the following is general advise.
Aluminum stretches more under load than steel. The higher RPMs you run the more load on the rod. Because of this you need to run more piston to head clearance with aluminum rods than steel. Most SRT pistons are pretty far down in the hole to begin with so I don't see this being a problem, just something you should be aware of when building your motor.
In the short term, say over the course of a race season or 2, the aluminum rods can be stronger (not to mention much lighter) than steel because of there shock absorbing properties. That being said, there fatigue life is generally shorter. So, for high horsepower / high RPM racing applications (top fuel dragsters use aluminum rods) they make sense. But, for a street car that you want to get 100k miles out of, steel is probably better..
As far as thermal expansion and contraction goes, I don't see this being an issue. It certainly won't cause piston slap, if that is what you were saying. Piston slap is a function of piston to cylinder clearance, not connecting rod length or connecting rod expansion and contraction.