In a full eight yard kilt, the 10 oz does ok, but it's not ideal. I would say order it only if:
1) you are really committed to having that tartan, and having a custom weave is not within your budget
2) you are fine with the fact that it will be a light weight kilt

One of the differences between a light and heavy weight kilt I have found is that the light weight wool tends to wrinkle a lot easier and so you'll have to press the kilt much more often. I hardly ever have to repress the pleats in my heavy weight kilts.

And regarding No. 1 above, have you considered all your options as far as a custom weave of the tartan? If you go with a lower yardage kilt, it does not have to be that much more expensive.

I don't know where you plan on ordering your kilt from, or what price you were quoted, but just for the sake of comparison, at the Scottish Tartans Museum gift shop, our 10 oz light weight 8 yard kilts start at $475. While a 16 oz custom weave 8 yard kilt is $770, you can have a four yard box pleated kilt in custom woven heavy weight cloth for only $495, which is only $20 more than the 8 yard kilt in light weight cloth.

If you look at my personal kilt making page, on the order form, on the right hand side, you'll see a price breakdown of the various styles of kilt I offer, with prices shown for custom weaves:
http://newhousehighland.com/kilt_order_form.php

Between getting the tartan you want and getting the weight you want, the most important of the two issues is the tartan, in my opinion. However, there is really no reason not to have both, so long as you can budget the bit of extra expense for the custom weave.

I just wanted to make sure you explore all your options and ultimately end up with a kilt that you are really happy with.