Hope your learning is going well.
I’m sure you’ll get every possible answer there is for this, but here’s my 2 cents.
Firstly, need assume we are comparing same style of kites, as power difference can be huge for same sqm.
As a learner power is your friend, most need a lot of power to keep momentum going from starting.
So yes, you are going to need a bigger kite.
Depending on your weight, the winds you kite in and other factors like sea state, you are likely to find 2m between certain kite sizes to be a lot. However, at other parts of your kiting spectrum 2m won’t feel like much.
For me 10m to 12m is a world of difference compared to 13m to 15m
I would advise a little planning of what winds you want to kite in, the style of kiting and the amount of gear/budget you want to allow.
Eg. 2 boards & 3 kites, moderate winds – freeride. Or if you want to travel, you may need a bigger range of gear, similarly if you have long spells of light winds in your area. For most of us we want to go kiting when we have free time, so a good range of kit is going to allow you more chance to go out when you have the time.
Assume your 10m is a good kite – this is because it is now the datum, then you need to plan around this.
Guys around you weight I have kited with would maybe have 9/12/15m Kites, hence your 10m makes your planning slightly different, maybe 8/10/13m. Many don’t like to go for big kites and in Scotland (assume that’s where you live) you will be blessed with plenty of wind!
Let us know what wind range and style etc. you want to aim for and hope I can be a little more specific.
Here’s a thread with a great graph of wind/kite size, by Peter Frank: