I have been going up in both size, weight and magnification from my first scope onwards.
I started with a 60 mm Mirador in the 1980s, when most folks had a Kowa TS1. Unfortunately, my sample was a bit of a lemon and never showed fully satisfactory images. Maginification was 27x. That was followed a dozen or so years later by Alexis's favourite, Nikon ED 78 A, first with a 38x Wide eyepiece, later other WA's and a 25-75x Zoom.
When the ED 82 A was introduced, I upgraded again, but now the improvement in image quality as well as growth in bulk were relatively minor. Both Nikons were cherry samples with superb image quality. 25-75x zoom was by far my most used eyepiece on these, especially on the 82. With the zoom, I was using magnifications in the range of 50-75 quite a lot, and came to conclude that for my kind of birding, I could not be satisfied with a smaller objective size simply because it would not take magnification well enough.
The Nikon held its ground against stiff competition for many years, but finally had to surrender when Swaro introduced the ATX 95. If Kowa would have come out with their extender for the 883 before the ATX, I probably would have gone that route, but in hindsight I'm happy that did not happen. So now my scope weighs 2.2-2.4 kg (depending on whether the Extender X is on it or not) and maximum magnification is either 72x or 120x. I'm not going to get a smaller scope even for an alternative, as for me its worth carrying around the weight and size for the better view.
As advice for others, though, I'd tone it down a bit and suggest just getting the biggest size you are comfortable carrying. Keeping in mind that the tripod needs to be good, and that there are options available for making carrying the kit more comfortable.
Kimmo