Actually Jonathan you have now shown a fairer account of the simulations, this shows a more realistic picture so well done to for that. The deflections shown though in the grand scheme of things show very little in the way of movement between them all looking at those figures. Now if i were to build again i would 100% go for linear rails supported on the biggest bases as possible, in a small desktop machine for pcb and plastic work then round rail would be fine (only if it was the cheapest and only option).

Thing is a lot of people expect their routers to be milling machines as well, only in this case you would need to worry about expensive linear movement. For most diyers the need to be honest about what they want to use there machine for and build accordingly. If they can not afford that then they have to live with the compromise or save up and wait a bit longer.