Here's how the last three bluetooth headsets went for me:
1) Jawbone I - Really hate how it needed two hands to hook it on my ear and how it flopped around and was hard to get it to touch my face properly.  Buttons were extremely hard to press, especially when it was on your ear where it could be painful.  Made the mistake of putting it in my coat pocket where the ear loop broke off and in the process messing up the earpiece such that it wouldn't hold the replacement earloop.

2) Plantronics 925 - I love this headset.  Really small/light with great selection of soft ear inserts for that perfect fit.  Easy to put in ear one handed.  Came with a custom hardcase so that no need to worry about breaking it in a pocket; bonus was being able to recharge the earpiece using the case's built-in battery.  Biggest drawback was noise cancelling performance.  I bought the Jawbone prime not because I didn't like the 925, but, because the Jawbone was 50% off when I bought it along with my new iPhone and two-year contract with AT&T.

3) Jawbone Prime --
I had to use an earloop; but, it's now easy for me to put the earpiece on my ear one handed.  Wish the various hard rubber ear inserts would have allowed me to use this earpiece without the earloop (since the earloop is vulnerable to breakin.)  Still not as secure as the Plantronics 925 in my ear, but, it's acceptable.

Buttons much easier to push.

Noise canceling microphone is excellent; no complaints.  This remains the biggest selling point for the Jawbone.

Wish the speaker volume would go louder (similar complaint with the Plantronics 925).

Biggest complaint remains the vulnerability of the earloop when the earpiece is not in use.

So, I'm currently using the Jawbone in the car and bring the Plantronics 925 with me when I'm on the go (which usually means I'm not worried about road noise).

If I had to chose between the two, I'd go with the Jawbone Prime; just avoid putting it in your pocket if you need to use an earloop.
Here's how the last three bluetooth headsets went for me:
1) Jawbone I - Really hate how it needed two hands to hook it on my ear and how it flopped around and was hard to get it to touch my face properly. Buttons were extremely hard to press, especially when it was on your ear where it could be painful. Made the mistake of putting it in my coat pocket where the ear loop broke off and in the process messing up the earpiece such that it wouldn't hold the replacement earloop. 2) Plantronics 925 - I love this headset. Really small/light with great selection of soft ear inserts for that perfect fit. Easy to put in ear one handed. Came with a custom hardcase so that no need to worry about breaking it in a pocket; bonus was being able to recharge the earpiece using the case's built-in battery. Biggest drawback was noise cancelling performance. I bought the Jawbone prime not because I didn't like the 925, but, because the Jawbone was 50% off when I bought it along with my new iPhone and two-year contract with AT&T. 3) Jawbone Prime --
I had to use an earloop; but, it's now easy for me to put the earpiece on my ear one handed. Wish the various hard rubber ear inserts would have allowed me to use this earpiece without the earloop (since the earloop is vulnerable to breakin. )  Still not as secure as the Plantronics 925 in my ear, but, it's acceptable. Buttons much easier to push. Noise canceling microphone is excellent; no complaints. This remains the biggest selling point for the Jawbone. Wish the speaker volume would go louder (similar complaint with the Plantronics 925). Biggest complaint remains the vulnerability of the earloop when the earpiece is not in use. So, I'm currently using the Jawbone in the car and bring the Plantronics 925 with me when I'm on the go (which usually means I'm not worried about road noise). If I had to chose between the two, I'd go with the Jawbone Prime; just avoid putting it in your pocket if you need to use an earloop.