Thanks again for all the input. I didn't realize I could use the same bar for all kites (if I buy Cabrinha kites), which would save some money and weight when traveling. I will be looking for a 9m Switchblade (or maybe some other compatible all-around model, if there is any in Cabrinha's line up).
My first fully independent session was on 17m and maybe that's why I fell in love with the 17m haha (I was even riding at full power). The kite was Airrush Lithium Progression and was a peace of cake to relaunch (I only hated the inflation system, you have to inflate the struts separately). The big kite is slow but somehow predictable for a beginner and forgiving when losing control or falling (whereas small kites fly all over the place and crash violently).
Also, there is always so much space on the water when the wind is light, as many riders either won't bother or don't have appropriate gear. And that is great when you are still a newbie.
However, it seems like with more experience I will be getting the same results with a 15m.... I just don't want to end up underpowered on a 15m and upset that I didn't buy the 17...
Here's the thing: a 12m should get you up & planning on your board in 12 - 13 knots & fully powered in 14 - 15 knots. A 15m will get you planning in 11 - 12 knots & a 17m in 10 - 11 knots. The 12m will remain useable up to about 20 knots, but the bigger kites will start to feel uncomfortable much earlier. The additional low end you get with a big kite is marginal, but the high end you lose is significant. Using a light wind board - wider & flatter rockered - will give the sam kind of additional low end as a big kite (this is especially true of a directional board &, of course, a foil, but that might come later). The low wind board will cost a lot less than a big kite & it's easier to switch boards than switch kites during a session.
You don't really want to be traveling to any kiting destination that requires you to bring a 17m kite ... or a light wind board really. If you live somewhere that regularly has days with consistent 10 - 13 knot winds it might be worth having a 17m. Anything other than that I wouldn't bother. A 15m wold be worth considering if you are going to have a lot of days with 11 - 15 knot winds.
It all depends on your local conditions. When I was riding TT only, 70kg, 15m biggest kite. I wish I had bigger kite so I upgraded to 17m and was happy about it.
Our conditions are light wind most of summer, so light that 17m -- 15m made difference for light rider. Yeah I got super overpowered if wind picked up and that is not fun, but usually the wind don't change much on those light wind sea breeze days.
So if you have $$, local conditions are mostly light (10-12kts), only riding TT board --- 17-21m kites make all sense to me.
Alot of different opinions here but the most important things is your local wind conditions.
You're new to the sport, and want to maximise your time on the water. Especially if travelling.
You'll end up dealing with winds 10-25 knots, and feeling comfortable in them.
I'm same weight as you, but been kiting since 2002. It's important to use similar kites across your quiver in the first years.
Keep the 12. Get a 9 switchblade. and a bigger 15 or 17m 3 strut kite. I'm not up to date on cabrinha kites, but they must have a lightweight 17.
A 55cm bar. Keep your board, and ride it.
3 kites, 1 bar, 1 board.