I'm in the market for a multi effects pedal which can cover sounds from rock to punk and from blues to metal. These are the 2 I've narrowed it down to unless there are other similar stomp box multi effects pedals out there.

Which is best?

Boss GT-8.
Ibanez RG321MH (Air Classic/Tone Zone)
Fernandes Telecaster (Twang King/stock bridge pickup)
Blackstar HT-20 (Scumback 55 speaker/ Tung Sol tubes)
TC Electronic Nova Repeater
Lava Cables Clear Connect, Soar and Mini ELC
My vote is on Digitech.

I used to own a Digitech GNX3 and I wanted to upgrade to something newer. About a year ago I bought the GT-8 and had it for a month before I traded it in for a GNX3000. The GT-8 has great sounding effects with great parameters and the dual amp thing was cool, but I just could not get good overdrive and distortion tones because of the limited selection of amp, distortion box and cab models and the eq was weak. Wheather I hooked it up to my amps or to a mixer it just sounded like crap and very unrealistic. Maybe I was doing something wrong or may I didn't give myself enough time to really try and tweak it, but I think I'm pretty good at that.

The GNX3000 is great at reproducing different amp types and the tone is awesome. Some of the effects are not as lush as the GT-8 but you probably don't use chorus, flanger or phaser all the time. So I stuck with the GNX3000 cause of the easy of use, the numerous amp, cab models and the parametric eq and lets me tweak the hell out of my tone on each preset. I love it for doing my cover band thing. The only addition I use to any modeler is my Bad Horsie II wah, I like that it turns on and off by me only putting my foot down or taking it off.

Try out the Digitech stuff for modelers and see the difference. It's funny, as for single effects I prefer BOSS and will not even look at Digitech for compact effects.
i have a boss gt8, and for what you want to do, id recommend it! i wanted a multifx pedal for its versatility, so that i wouldnt have to buy more gadgets for quite a while. Ive had it for over a year, and im still learning about all the cool functions that it can do. Its a great pedal, and very solid. I dont think you will be disappointed. I havent tried the digitech, so i couldnt help you there. I think digitech is just full of problems though (i read it al lthe time in reviews etc).
well , good luck!
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POD XT Live.....especially if you are using it for distortion or recording.......the high gain distortion on the GT is a bitt fizzy...
If at all you are looking at digitech you can look at the GNX....comes with 4-track recorder Usb interface...
GT8 definitely. The only decent stuff Digitech put out imo are their old rack processors (2101, 2120, 2112) and the GNX 3000.
I do own both pedals and they are both very amazing pedals. The digitech I do have to say hands down is a better choice. The boss has great tone but its limited to what you know about the pedal. From buying both used i learned that the boss you need to have an operating manual to understand where the bells and whistles are. And then after that understanding how each knob and parameters work. Its just so time consuming. I mean the wonders of youtube helped me figure out how to use it within a day. But it still took a good couple of hours to dial in a tone. Now as for the digitech. Your isntructions are displayed right in front of you. Its so user friendly. It took me only like 20 minutes to dial in a tone because everything is labeled for you and you know exactly which knob is doing what. I never had to look up an instruction manual because all the amp models and tones are displayed on the screen and each of the 5 knobs have a role on how to use it. And the pedalboard function is great. Press a button and you can turn off and on a function at will.
So my overall choice is the digitech just because its more user friendly.
I saw neither. I've owned the Boss GT-6 and Digitech RP355. The GT-6 is similar to the GT-8. Anyways, I didnt like the sound of the GT-6. Sounded too digital. Last time I will buy a Boss multi effects unit. The RP355 sounded to muddy and couldn't get heavy sounding enough for me. Now the GNX3 on the other hand, has a load of gain for what I use it for. It gets very heavy sounding and can get quite loud too. Has a level knob on the back of the unit. The whole thing is made of metal so its pretty durable. One feature I did like on the RP355 though was the drums and the pressing down on the foot pedal to engage the wah. Other than that, I didn't like it at all. I've never played an RP500 though so I couldn't tell you if tis the same or not, I just know it has alot of the same effects and presets and what not as the RP355. If you can, I'd get a GNX3 or GNX4. Those are way better in my opinion.