Share with you what I had done in the past ...
I checked around on the web for quite a while before and then.
I ended up with the Line 6 Pocket Pod. Used it regularly for more than a year, although I had a Marshall amp. With MP3 player connection and loads of effects/amp modeling, it was a joy! I was on adapter power most of the time because this thing consumes battery power pretty quickly, less than an hour of continuous use, I think.
Then I learn about the Korg PX5D. I guess I wanted drum loops instead of using a metronome. Sold the Pocket Pod and bought a new PX5D. The modeling/processing on the PX5D is better, as it sounds to my ears. Batteries on the PX5D lasts longer.
Not long after, I got news of the Boss MicroBR. A different gadget altogether but I wanted a better phrase trainer and the MicroBR is so much better than the PX5D. I purchased this online and it cost $100 less if I were to buy it here. I find myself using it to record straight from either my MP3 player or Youtube, sections of songs that I need to work on.
I still use the PX5D because it is a good unit to keep and the quality of the processing is really good. The construction is sturdy as well. I suspect, with a foot switch, you could probably use it live!
Get a good headphone, I must say, as the one I am using tears up easily and now the plastic has cracked. Use Eneloop or ReCyko batteries, they last much longer and is re-usable.