I was with Spark on VDSL until they discontinued all copper connections in my area. Chorus still support copper in my area though, and because fibre from the street to the house is not a straightforward matter in my particular situation, AND we use more data than 4G options allow, I've now got VDSL with Voyager. As soon as I can get fibre I will. Am just praying that's going to be possible before Chorus switch the cabinet off here.

They've been OK so far. It's been nice to have the phone answered promptly on all occasions bar one, and they are friendly & very helpful. My only complaint was them setting up an automatic direct debit for bill payments, in spite of the fact that I explicitly declined this payment option when I signed up by phone. They did that without my consent, using the provided bank account number I gave them that they said they needed to perform a credit check. However they were quick to fix that up when I rang about it. My only other issue was getting the email about the price increase, with a link to click to see how it would affect me. However on clicking the link it seemed to be about fibre connections, discontinuing contracts (I'm already on open term), stopping copper landlines (which I do not have) and I'm already paying $89 for my service (+ $10 rental modem). The FAQ said it was an email sent to affected customers only. I rang them and they said there'd be no change for me, so I'm not sure why I got it. The guy on the phone wasn't either. I was worried the soon to be removed "50/10 plans" might be code for VDSL, but thankfully it isn't - that's apparently an old fibre plan they used to offer. Re-confirmed copper isn't being cut in the near future with Chorus, and thankfully it isn't. 

The modem is a Huawei DG8245V (I believe this is for for both fibre & copper). If you're familiar with the old Huawei HG695 it's basically just the upgraded model of that, and feels very similar to use.  It's been VERY solid in terms of up time, and speeds are similar to my experience with Spark using their Smart Modem. I got less ping and better upload speeds with Spark, but the downtimes are comparable if not slightly better. The Voyager modem has a MUCH lower device limit than the Spark Smart Modem, and it doesn't seem possible to remove old devices in the web page (you can blacklist them but not remove them). This could be a problem if you have a lot of devices or replace devices often. I forget the device limit, I just remember it's low. It can get itself in a bit of a tangle using a VPN client I've found. Once the VPN is disconnected I sometimes seem to get ridiculously low speeds and find I can only have one or two devices connected. A reboot of the modem fixes it immediately. I don't recall ever having that problem with the Spark smart modem. That's really been the only issue I've had with it. 

Hope that helps.