I would say, Aeroline has the best bus service in Malaysia so far.
Although I have not tried NICE, but I think it would provide almost similar service with Plusliner, except that NICE has bigger seats with meal provided.
Even the Konsortium snoozer is not any better. Other than providing personal TV set to watch, I find that the seats and flooring is rather dirty. At least, Aeroline is almost leather-PVC-like seat; I felt cleaner throughout the entire Journey.
Moreover, it's promotion period now! And. i like it when they asked for feedback upon returning.