Well as Planning permission has already been approved. I can see how going around the bend will be better. Taking it into the round really will change the feel of the layout. I think it will be for the better. I think the one thing that might go in you favour is if the whole thing goes up in the world. Ie make the legs longer for the whole layout. That way you won't have to ben as much to get in to your modelling desk.
As you know me I have a great time tinkering with something as a train trundles around, in fact I forgot, today, and 3 hours later the train was still happy chugging around!
Now no rash decisions now!