I would not use the SL 5 unless I need it for one of the smaller local markets that use it for SD locals, but even those have the same programming in HD which can be received with the SL 3. The SL 3 is much easier to aim than the 5.
In answer to KAB449, the SL 3 and SL 5 both aim at the 101 satellite. The only time the 110 is used as an aiming point is when using the, almost obsolete, Phase III dish, which is only for SD reception in smaller markets like Knoxville, TN or Mobile, AL. There are other markets but these, I am familiar with. The SL 5 is usually installed in these areas, but only for SD. I don't know anyone who receives HD locals who even cares about getting the same channels in SD.