Think if it came down to a choice between Weideman and McKay, I'd be leaning towards Weids.
With Kreuzer, Phillips, Gorringe, Wood and Korchek on the list, in addition to Casboult, I believe a mobile, breakaway, leading forward will be more important than a 200cm contested mark / part-time ruck. Our forward line for the last few seasons has been very static, and McKay looks to be the type of forward that uses his height to bring the ball down in a pack situation. We need to transform our forward line and bring it into the modern era - everyone working in concert to create space for forwards to lead into, and a range of targets to reduce predictability. McKay, though he may be of a higher quality than our current talls, would give us nothing we don't already have.
Not to say that McKay won't be a good player, and if Weideman is gone I'd still be happy with McKay - but in terms of our forward line dynamic, Weideman appears more suitable.