XT Live and the GT8 are great pieces. I have the XT live by Line6. There are so many possibilities it can be frustrating but Line 6 has a good support forum and tons of down-loadable tones from other users and the Line 6 people. You can also download Riff Tracker for free and for a monthly Fee($10 a month I think it is) you can download lessons and background tracks. The unit is updatable online from Line 6 using the USB port so any improvements to the software are free. It works great live but also an awsome piece for studio work. With the USB connection you can record direct to the computer and all settings on the unit for tone can also be done on the computer using the free interface software( no bending down to make changes). Changes can be done on the unit too if on stage without a computer. It offers 32 preset channels and a-d. So you have 1A, 1B, 1C and so on to 32D for pre-ste tones. So say you are going to a gig and you have a 10 song set. You can set all your tones in the order you plan to play the set up prier to the gig. Now your first song maybe has a tone for the rhythm section and a tone for the lead. Set switch 1A for the rhythm and switch 1B for the lead. Now just hit the foot switch as needed. It's much easier than a pedal board with 5 different pedals. It also has a wah and volume combo pedal. Don't expect the amp models to be exact. Hell the 2 of the same amps don't sound exactly alike but you can still pull of a ton of good tones and you don't need to buy a million dollars worth of amps and pedals.

Holly crap I should get a commission from Line 6.

I can't tell you mush about the boss or Digi-Tech versions but maybe someone else can.

Hope that helps.