Which PSU should I get ?

Actually they are not electronically identical.

The 750TX V2 is made by Seasonic and the 750TXM is made by CWT.
They are rated at the same output though as both supply 62 amps on the +12v rail.

The 750TX V2 gets a 9.5 jonnyguru score.

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=230

The 750TXM only gets an 8.3.

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=254

I would get the 750TX V2 myself. There are better modular power supplies in that range for the money than that Corsair if you really want a modular unit.

The OCZ ZT 750w is only $90 after rebate and scores a 9.0 from jonnyguru.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817341052

http://www.jonnyguru.com/modules.php?name=NDReviews&op=Story&reid=262
 

I think this one is better than either of the Corsair's you've listed:

XFX 750W PRO750W XXX Edition Single Rail ATX 12V 62A 24PIN ATX Modular Power Supply 80PLUS Silver $124.99 CAD ($104.99 CAD After Mail In Rebate)

http://www.ncix.com/products/?sku=62224&vpn=P1750BNLG9&manufacture=XFX

It's more expensive at newegg.ca:

http://www.newegg.ca/Product/Product.aspx?Item=N82E16817207016