IMHO the long loose followthrough is "better" as it will keep the pitching motion in line with the target longer and help with accuracy. A release anywhere along that line will be more likely to be on target (at least side to side)
But technically either release is valid IR follow through. Generally I have seen the younger/newer to IR pitchers follow through to the opposite shoulder because it helps with the motion. As they mature into the motion it tends to get longer and more relaxed.