Both these plugins are close clones of each other.
I bought and used IgniteWoo's Gift Certificate Pro. I couldn't
even purchase Smart Coupons, Woothemes site rejected my credit card (never had that happen before, or since, on any website).
With Ignitewoo's Gift Certificates Pro plugin, one bug I immediately came across was that the coupon description field (for the admin's reference) doesn't save.
What we didn't get:
We wanted a record of any gift vouchers/coupon codes in the
user's My Account area, so people can log in and view their coupon code/s at a later date rather than be forced to trawl through their emails. Nope. We were also hoping gift certificates could be downloaded for printing (Groupon style) because emails don't print well/consistently as everyone knows. Nope.
The reason: these plugins don't generate anything download-able or viewable on-site by the user, just a coupon code delivered in an email which they then apply at checkout.
As far as I can tell, only (the $99)
http://www.woothemes.com/products/pdf-product-vouchers/ produces a PDF
with a voucher integrated into WooCommerce's user-facing account area (for re-downloading).
Gift Certificate Pro works, it's just not what I would call, IMO, a gift certificate plugin which is surprising given its name, more of a coupon code generator with an emailer.