I only do boxing and I am a heavy puncher.
For me the Fairtex bgv1s were not good on the heavy bag at all. Every time I used them I had bruised knuckles. All the had going for them was the compact size.
I had the Fighting Sports Tri Tech as well they are way more protective.
If you want to do heavy bag work I would recommend F/S. If you want fairtex I would go with BGL-7. Those are amazing, but are lace-ups.
Check my auctions on Ebay ending on 05/19/13 (Sunday)