I’d say both are really interesting platforms,
what I really like about both is the strong sense of community that surrounds them.
being open, flexible and community oriented, I think is largely more important than the technical differences ( esp. if you are not a programmer)
so, I think investigating the communities, and what they are doing, saying, and seeing which ‘gels’ with you the most, is probably the way to see which is going to work for you.
at the risk of generalising (so, I don’t claim this is true for all), but my observations are:
Norns:
it’s newer, it’s about possibilities… it has a strong community
the community currently feels more ‘technical’ to me than the Organelle … but thats likely the nature of it being quite new. (10 months old?) and could very well change as it matures.
I think Norns strength is being part of the Monome ecosystem, tight integration with the grid, later with Crow, and other Monome products - seamless integration, using their full potential is a really appealing combination.
but, for those not invested in Monome, adding a grid adds $700, so a frequent question is:
Can I use it without a grid?
this I think is a very tricky question… technically the answer is YES.
but what the question is really asking is:
how many / what type of scripts am I going to be missing out on?
how many developers are going to support non-grid users?
this we will only know as the community develops, the more users without grids, the better they will be supported. for now, its seems like more complex scripts, esp. those with sequencing elements, will require a grid, and those concentrating more on fx/synths won’t.
I repeat, I’m not saying a Norns requires a grid - rather currently, you need one to open up its full potential. (e.g. I doubt there will be a version of MLR for a non monome grid in the short term)
this is not a criticism … the Monome grid is lovely, its fantastic to have a platform which allows its potential to be fully explored.
technically, Norns has more resources/cpu than the Organelle - which I think will become more apparent as Norns matures. but, as always its down to what you do with them 
Organelle:
self contained, with a fixed form (albeit limited) factor that all patches use, and pretty simple.
I believe Pure Data (and visual patching generally ) is much easier for non-programmers to pick up, and ‘dabble’ with. esp. since Norns splits patching into two parts Lua for control and SC for audio.
the community is more mature than Norns… so you can see, despite the limitations, the Organelle has been pushed in many different directions , for me, this makes it feel really quite a vibrant place.
the form factor is limited (*) , but what I love about it, is I know its the same for everyone, so as a patch developer , I know what I have to work with, and I know everyone can use my patch.
(sure I add midi learn, and orac 2.0 has a ‘remote interface’ , but this is alway optional!)
also I love its cute/small form factor , grab some headphones, a usb battery pack, and play it on the sofa.
for some reason I think its simplicity in form factor, spills over to the patches (probably due to the C&G influence) , generally they seem playful, don’t take themselves too seriously.
(*) hmm, I keep on saying the form factor is limited, in fairness, the norns is also limited…
norns: bigger display, 16 brightness levels, 3 encoders, 3 buttons
organelle: small b&w display, 1 push encoder , 5 pots, 25 keys , 1 tristate led
if your invested (or want to be!) into the Monome ecosystem, I think Norns is great, its got huge potential, seems like an obvious choice.
if you want something self contained, its not as easy…
I think, for me, the Organelle currently has the edge, its cheaper, its simpler, its self contained, and its more mature…
(note: I’d love to review this in one year… when norns will be more mature, more scripts etc etc)
but as said at the top, and by others…
if you want an open/flexible platform, which you can tweak , either is great - both are really down to what you make of them!