The 14x29 is literally a different board from the 14x30 Glide. It is a completely different shape, and they are designed for somewhat different purposes and aimed at different paddlers.

The 14x30 is a huge board. Probably far too much for someone your weight. You don't want to be trying to push around vast acres of foam you don't need out in the water. You'll find it frustrating and hard to control in wind.

By contrast, you'll probably like the 14x29 a lot. Try and get a demo.

I'm a similar weight to you and far prefer 14ft boards. There really is no reason to get a 12-6 unless you are too weak to carry or load a 14, or you are going to specialise in certain race formats that require 12-6 boards. Even most women would be better off on a 14 IMO, but 12-6 has become, for largely historical reasons, the "board size for girls", so it is this gender stereotyping I think that keeps 12-6s afloat. Girls buy 12-6s because girls buy 12-6s. And some of them can't carry 14s, or think they won't be able to.

Many of the paddlers on a forum like this are expert. To them a 29" board seems massively wide, so they'll often recommend a narrower board. But actually, for most people, especially in choppy conditions, 29" wide is faster and more comfortable.

But demo some boards for yourself. It is very hard to make recommendations for other people. Height and weight are only two factors in a very complex equation when matching person to board.

Dave at 78kg you definitely don't need the 14 x 30* Glide. The 14 x 30 isn't just a blown up 29...they are very (very) different shapes.

A 14 is probably a bit more versatile choice for around Melb and the bays than a 12'6, especially if you decide you want to go downwinding. At your weight in Naish boards you would be very comfortable on the 14 x 29 Glide. I'd also suggest you look at a 14 x 28 Javelin, you'd probably be comfortable on one of those too.

IMO you should definitely take a good look at the 14 x 28 NSP/DC and the 14 x 27 lahui kai, a couple of the 14' SICs as well. Prob worth you checking out the 14 x 27 and/or 14 x 28 Starboard Allstars. All those boards are surprisingly stable, they all feel different to each other. You're a long way from huge so there are a few options out there for you - especially in and around Melbourne. Demo/try as many as you can get your hands on.

(*the 14x30 Tern mentioned is mine...I've got almost 50kg on you and I have some balance issues. )

Thanks for the feedback guys and it sounds like I will have to try and get time on a few boards to see which one I prefer even though I prefer the Naish models at the moment.
I will demo more 12'6 boards and straight after try a 14 29 wide and feel the difference and see how they suit me even though chances are I won't do any DW any time soon, but you never know things change. The biggest problem is getting a good demo of different models and sizes in the one spot. i will demo the Naish models at Jacks boards but will need to go to KR, Zu, SHQ, Mordy's, to try NSP, Starboard, Sunova, Bark, and anything else worth looking at if they have a demo board at the time.
Best to think about it now and take my time looking around asking questions and buy much later this year so I don't need to sell the board after a few months.