I've seen both models - the will likely be dependent on the length of your sales cycle. It's hard to comp an inside sales rep on an opportunity won if the opportunity isn't going to close for 6 months or a year. If it's a 30 day close it's much easier. If you do have a longer cycle and need to comp on pipeline, then make sure the sales rep has to accept the opportunity and measure the % of opportunities closed by rep to ensure they aren't just accepting any deal.
@Matt Amundson/Matt Amundson (not sure which is his active account) may also be able to help <--he managed BDRs at Marketo when I was there and is now even more awesome at Everstring 🙂