Any of the packages and individual components listed will work great in the LT-40.

The basic S3004 servos are plenty for any trainer plane and most 40 and 60 size sport planes.
The S3152 digital is more powerful, but only a tiny bit faster.

I would buy the radio system with the S3152 servos because it is only $30 more and the price difference buying the servos alone is about $20 each. Then I would buy four standard ball bearing servos for $10 to $15 each (S3004 is fine) to go in the LT-40 and save the $35 each servos for a future model.