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The automatic transmissions, if that's considered, are completely different between the two vehicles.
The QQ has a Japanese Jatco CVT, and the Kadjar has a German Getrag dual clutch transmission, similar to what's in e.g. a Ford Kuga.
The boot of the QQ may be a bit smaller, but I would still not consider the Kadjar boot to qualify as "big".
Many SUVs have bigger boots than the Kadjar, eg Honda, Subaru, Toyota, Ford, and even the Dacia Duster.
And then most mid size wagons have much bigger boots.

i will go for kadjar. i prefer more power and torgue from  the 1.6 turbo diesel than the 1.5 dci. 
i like more the kadjars shape than QQ shape, is more modern and eye catching. More boot in kadjar .
i was between kadjar 1.2 petrol and 1.2 petrol QQ

In the Auto Express a couple of weeks ago they showed pics of the 'new' facelifted QQ and I must say I was impressed. It will be interesting to see what Renault pull out of the bag to combat this (if they ever get round to pulling their finger out). As much as I love my car it no longer stands out in the crowd as it once did. Looking decidedly tired at the moment.

The kadjar boot is minimally bigger than that of the qq, if that few litres is important then you need to step up a class in car size. My tyre report is accurate, this is the info the OP wanted. Both QQ in 1.6 and Kr in 1.5 eat there tyres in 13k and 10 k respectively, rears on both cars looked like new at the same point in time. It's fine saying don't go for conti's but Renault have done and there aren't too many alternatives around yet. 
The general feel on the old site was to budget for new tyre dam expensive tyres, at 12/13k.

PW had a sit in the latest QQ a few days ago, way better than it was 4 years back, but for me they have to have sorted out the noise issue. The old car had the noisier 1.6 dci, but I got transmission whine and unbelievable rattling from stones and gravel as if there was no underbody damping and no internal sound buffing.    It sits in top spot so far but will need to look at reliability reports as it was way down the last time I looked.

Well, probably the previous batches were poor quality. My Conties are noisy, but are looking like new (and perform good enough).
 By the way, what infotainment system is the QQ using?

It's the Nissan Connect so no Android Auto/Apple Carplay. It's a bit dated now and from what I've seen the KJ's map graphics are far better.