Well IMO better is not the word to use. I would use the word different. It is way too generalized to call either of them better (vgt vs non vgt). Their are different strokes for different folks. VGTs have come a long way with the new ideas, innovation, availability of parts, better tuning, and better knowledge on what mods match up best.
With that said vgts will always have their downsides... sticking vanes, sticking unison ring, more expensive than non-vgt, etc... but with our knowledge about the turbos I have seen zero problems from people who buy our turbos. Most of them have egr deletes, ccv delete, better tuning, use better oils, and maintain their trucks better. VGTs will run a slightly higher BP ratio... that is why they spool faster (its a byproduct and becomes a slight restriction)
On the other hand non-vgts do have their downside... lol... it is the fact that they don't have the vanes to help them spool up quicker. Tuning has come a long way but if you take any two turbos (vgt vs non vgt) of very similar options, in general, the the vgt turbo is going to spool up quicker, and the non-vgt will flow more air up top and not choke out.
VGT will spool on a more exponential boost curve
Non VGT will spool on a more linear power curve
VGT will usually light off sooner in the RPM band
Non VGT will usually light off later in the RPM band
VGT can be harder to tune (especially in compounds)
Non VGT have less ability to tune (no vanes to adjust)
VGTs are still limited in size (no 80mm vgts out there)
Non-vgts have many more options
I can't tell you if it is worth it to switch, depending on the size of your current setup you might not see any power gains in peak power but you might see a change in how the power comes on and where you make your power. IMO it will just come down to how you want your truck to drive.
I hope that makes sense without coming off too biased.
