Which ever one your insurance will cover. <img src="i/expressions/face-icon-small-wink.gif" border="0">
I have had an old Hill/Rom and I did not care for it. Some people here swear by it. But I ended up trying the Electromed Smart Vest and I REALLY like it. (I don't like vest therapy, but the Smart Vest makes it tolerable). <img src="i/expressions/face-icon-small-smile.gif" border="0"> As my lungs get worse I like that I don't have such a hard time taking a deep breath with the Smart Vest, I couldn't do that with the Hill/Rom.
Electromed explained to me that the Smart Vest is an open system and most other vests on the market are closed system. This allows the air to escape when I inhale, so less resistance. Closed loop causes more pressure as you inhale, between your chest and the vest, making it harder to take a deep breath since there is no where for the vest air to escape to.
But if you can, see if you can get a free trial from several companies so you can find the best one that works for you. Most companies are very happy to let you do that.