ETrade and Zions are both simply pretty user interfaces that sit in front of a wholesale bond exchange from BondDesk Group. 98% of what you see on these sites is NOT their own inventory. They are simply reflecting a marketplace that many entities have access to. In some cases, a broker might have its own inventory on hand and be able to show that to you. It's such a small consideration it should not factor into your decision.

If you are serious about buying and selling individual bonds, then what I would suggest you do is use three tools:

1) Interactive Brokers (IB), because you can simulate good to cancel limit orders and it minimizes your intervention and hassle in trades that may take weeks to play out.

2) E*Trade, for access to Moody's research and in order to see the BondDesk order book, which will quickly help you to see whether your trade on IB is getting through to BondDesk. If not, there might be some way to place multiple trades in multiple accounts and have that force the bid or offer onto an exchange. I have not tried that.

3) Learn to use FINRA TRACE, because that will tell you where the real market for the bond is.

The River Rock bond yesterday was being quoted 66 to 80!!! My broker quoted me 78. I was able to use the above tools to see the real market was 68 to 69.5, if you were a stingy buyer.