With Inuyasha ears, go for small, triangular, and set far apart on the wig. And yes, I do agree with the fur making the ears too "bunny-like". A lot of people who know zilch about anime usually assume an Inuyasha cosplayer to be either a "cat" or a "rabbit"...Also, Inuyaha's ears are somewhat "folded"...don't know how to describe this the right way, but go find a good headshot of the dog demon and you might see what I mean. ^^;
The wig...yes, finding the right wig for him is rather hard, I agree. In fact, none really exist that would be perfect for him, you have to style and alter to get it done right. His bangs are very "fluffy" and poofed out, and extend farther back than most wig's bangs are set. Not to mention the length and thickness of his hair, in general. You might even have to use extensions for him. I did see one good Inuyasha-type wig made, but it was way too short and extensions would probably have been needed if you want to get the length part accurate. Getting his wig commissioned might cost a good bit...even a wig artist knows it's a complex design with a lot of hair involved. ^^; But if you want to try to style it on your own or something, go for it, and keep lots of reference pics handy. Though wig styling isn't as easy as it sounds, I found out the hard way. XD
*~Hime no Toki~*
2014 - Upcoming Conventions :
Anime Weekend Atlanta (GA) - FandomCon (FL)
Upcoming costumes : Princess Garnet (coronation gown) from FFIX, Edea Lee (various costmes) from Bravely Default, and more!