What is the best Leman Russ variant?

Starting to build my guard army and picked up my first two Leman Russ tanks, was wondering what variants I should make them? There's so many different options where I feel they can all be valuable but at the same time I feel like there are some thah just seem a lot better? So to the community I ask, whats the best variant?

Also what do you think are the best secondary weapons to put on them?