The Korg AX1500G has some of the same features as the Vox ToneLab ST; however, the Korg AX1500G does not have a tube in it. It does have a preamp making it ideal for direct recording and feeding into a P.A. system.
This unit can also be ran into a guitar amp, but you will have to set the tone settings (treble, mid, bass) in accordance with your amp settings so you don't have too much tone clashing with your amp.
This effect processor also has incredible amp and speaker cabinet simulators as well as killer distortions and effects. The expression pedal can be assigned to wah, volume, and uni-v effects.
The stereo outputs can drive two amps for left and right. When used with stereo pan delay, the sound will bounce left and right producing a killer "ping pong" effect. There is no USB port, but this unit sounds great!
The head phone/line out jack can still feed into a P.A. mixer and recorder because of the unit's unique "COSM" technology.
Boss has upgraded the ME50 to the ME70. The ME70 has same effects, but the ME70 has a built in loop effect and an extra foot switch. The ME50 has three foot switches while the ME70 has four. Both have an expression pedal that operates wah, volume and modulation effects. Both units are all knob based. This makes these units incredibly easy to use because you don't have to rely on cursers.
The Vox ToneLab ST and Korg AX1500G do have knobs but mostly rely on cursers for programming. The Vox ToneLab ST is built to be programmed, just set it and forget it. The Korg AX1500G is the same; however, you can set individual on/off switching of effects, but you have to get into the mode to activate it.
The Boss ME50 and ME70 are the opposite. They are meant to be set individually but you can also program them. The knobs for the delay are useful for special effects because you can adjust delay time and feed back controls in real time, making it great for unique delay effects. Distortion and other effects sound great!