Got a new 5D3! Some questions here!

So I'm happy as can be with my new five dee mark three (hey it rhymes!) but I've got a couple of questions:

Regarding battery grip, is there really much of a reason other than sealing and "how it feels" to buy an original one instead of an after-market brand? I don't normally use the battery grip unless I'm shooting paid work (which doesn't come very often nowadays for someone in the Army anyway).

If I go with the after-market route, are there any recommendations? I see 50 bucks and 80 bucks ones on Ebay, what are the differences? For some reason they have the "vertical" designation on both prices.

Anyone know if older Eye-Fi cards work with the camera?

And as far as eye-fi goes, does anyone know of a solid workflow for me to bring my images up onto a projector (set on slideshow) with the understanding that maybe range is an issue? A medium sized banquet hall with maybe 20 tables.

Thanks for your time!

I have a 3rd party grip and an OEM one(I'll be selling the the 3rd party one).

My 3rd party is an exact physically looking copy of the oem, some controls(locations as well), metal plates inside, even the rubber grips feel similar . The only real difference is the plastic outer shell and how the button feel when pressed(bit harder).

I was plenty happy with my 3rd party grip and only picked up the OEM because I'll be hanging it by the grip when I use a dual sling as my other body will be mounted to the telephoto, i think the 3rd party would do fine still but just to be safe the metal shell on the OEM will handing hiking around supporting the camera. lens and itself better.

Not all 3rd party are built as well others, any of them that use metal inside should be good for normal use.

Oh, sorry don't know about the Eye-fi, I use the PQI card because all I care about doing is instant sharing, but there's plenty of people that do use them I'm sure can spread some light on now both the new and old ones work on the 5DIII.

Well I only shoot in urban environments without any issue of weather, and my previous 5D2 had a 3rd party grip anyway. Seems like it's not a bad idea to get a 3rd party one then?

Any idea between the 50 buck and 80 buck options on Ebay?

http://www.ebay.com …Grips&hash=item​3ccd17460c

vs

http://www.ebay.com …Grips&hash=item​3a81007a26