Whoever won selection next week was virtually assured of a seat in Parliament because of the 18,000 vote majority built up by Mr Ryall, 49, who is retiring from politics to take employment in the private sector.
Dr Clark compared Mr Ryall's career path with another high-ranking former National Party MP, Rangitikei's Simon Power, who resigned prior to the 2011 elections for a job in business. Mr Ryall took over Mr Power's State Owned Enterprises portfolio.
National's Bay of Plenty electorate deputy chairman Paul van der Heyden said the first of three meetings, in which Mr Morris and Mr Muller faced the region's 101 voting delegates, took place last week.
Two more meetings will take place this week, leading up to the decision on June 3.
"We have two very fine nominees. It will be a very difficult decision."
Mr van der Heyden said initially there was quite a few people interested in becoming nominees but the numbers had reduced to two by the time the pre-selection process took place.
Mr Muller, 45, a senior executive at Fonterra, has been a National Party member for 25 years. He grew up in the Bay of Plenty and worked on his family's kiwifruit orchard before becoming a senior manager at Zespri in his early 30s. This was followed by his appointment as the chief executive of the avocado post-harvest orchard services company Apata Ltd.
Mr Morris, 33, has been a National Party member for 10 years and was elected on to the city council last year to represent the Mount Maunganui-Papamoa Ward.
He grew up in Papamoa and after graduating from Massey with a politics degree moved to Dubai where he trained bank and justice officials in English and customer service.