I have two Seagate desktop USB storage devices, a 500 gb usb2 and a 2 tb usb3.
They are not portable in the sense that you can just drop them in a pocket and go out the door. They sit on the counter top. I actually prefer that type. I rarely need to travel with it, but it's no problem to do so. Neither one has a built in on-off switch, I wish they did. Both have the type A jack. I think, not sure, that when you go from type a to a mini, you lose some speed.
The smaller one cost about $150 US, the larger one about $100 US, since the price of storage has gone down over time.
Not exactly what you are looking for, maybe, but I know some things about them from experience, which I'll gladly share.
I bought the 2 tb device because I thought backup images would fill the 500 gb device, but thats not going to happen, I'll never fill it afaik. I vastly underestimated how big 500 gb is. The one issue I have not yet got a grip on is win7 images . . . they are really big files, but I haven't yet done enough with them to say for sure that the 2 tb device is worth the price.
The 500 gb drive is about 6 years old, still works like a champ. (Fingers crossed, stay away, jinx) It's quirky, sometimes doesn't show up in win explorer unless I unplug it, turn it off, and replug it, but it never has failed to start.
The 2 tb device is about 1.5 years old. It works fine on usb2 capable computers, but is waaaay faster on usb3 capable computers. Just finished copying the same folder to both devices. It took 4 or 5 minutes from the usb2 computer --> the usb3 drive, but less than 1 minute from the usb3 computer --> the usb3 drive. I used the same cable for this, usb 2 type, I think. Also, the drive is sturdy. I dropped it onto a hard floor, still works fine.
Some have reported on the 'net that these enclosed HDDs have heat issues, but that's never happened here.
One insight I'll share is the value of having extension cables permanently plugged in to the usb ports on your desktop. That allows you to plug a usb drive in without having to climb around on the furniture. More importantly, imho, it saves wear on the computer ports. I try to keep a computer as long as possible. This win xp computer is about 7 years old, and the ports have gotten sort of loose, due to wear, I think. If those go, there is no replacement available any more. Also, not all usb sticks are machined to the same dimensions. I have a couple that are noticeable harder to plug in than the others. Seems like that would harm the usb ports on the computer.
There is a really good info site about USB generally at:
http://www.l-com.com/content/USB-Tutorial.html