That depends, If you can purchase the discounted Target GCs with a rewards credit card while shopping thru a reward portal for extra savings, you may do better buy the Target GC thru Raise (or other gift card reseller). For instance, Swagbucks offer 1% back for shopping at Raise thru their portal. I have a Discover card that pays 1% back and since I'm in my first year of being a card holder, they will match that cash back on my anniversary. So 2% back with my credit card. There's a discount code on Raise that will give an additional 3% off the price of a Target GC, So if I were to purchase a $500 Target GC, I would get it for $472.39. I would earn $9.45 from my Discover IT card and $4.72 from Swagbucks. The overall cost of the Target GC would end up being $458.22. That's a savings of 8.36%.
ETA - I just noticed that Target and Walmart GCs are not eligible for SB's 1% back on Raise. eBates does offer the 1% with no exclusions.