With regards to grounds for a divorce, it does not really matter which grounds you use but I would say it is better to use the less contentious grounds if possible. Invariably that would mean a separation period of at least two years. A lot of people think that if they petition their spouse for the fault based grounds such as adultery or unreasonable behaviour that will in some way enhance their claim and enable them to get more money out of the financial side of things or improve their standing with any children arguments; it doesn’t.
The fact is the ‘fact’ you rely on in your petition is a means to an end, it simply shows that the marriage has broken down and you should have a divorce. It will have absolutely no impact on anything else associated with the divorce itself such as children or financial matters.