The POD Go has the same amp, cab, mic models as the Helix, it's just a few of the effects models that are missing. Recently bought a POD Go, and getting some really great results from it, bought it to replace a POD HD500X (which is still a great option BTW).
The big question is how many effects are you running at the same time?
Only need 2 or 3 at once? POD Go is better. More than 4? Maybe a parallel signal path? HX Stomp definitely.
Will you use the amp / cab modelling, or are you just interested in the effects?
Both the Helix & the POD Go share the same amp & cab models. You can load third party IR's onto either if you want. However, if you're only wanting to use the effects, then go for the HX FX instead. You get all of the effect models from Helix without having the amp/cab modelling.