You wrote that you love shinglebacks -- do you live in Australia and see them often? More than likely you do not, so I'm just wondering why you "love" them. Is it how they look? I agree they are very unique-looking and interesting animals. I would love to have one (or two or three) also, but the thing to know about them is how expensive they are. For the average price of one shingleback, you could buy at least 10 Northerns!
I would say they are both equal in husbandry requirements, so it's just a matter of how much you are willing and able to spend on one animal. Along with that, although I wouldn't say they are hard to care for, it may be wiser to start with a less expensive BTS before making the significant monetary investment in a shingleback.
I hope my point came across the right way. I am by no means dissuading you from getting a shingleback; I just wanted to point out the cost and associated risk involved in purchasing one versus purchasing a Northern BTS.
Best of luck.
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Edward
Carpe diem