I previously used the Peregrine myself (it was my first dive computer) and switched to the Teric a few months ago for want of a compass amongst other features. Strangely you can fit more info onto the Teric screen due to the higher resolution, though I do miss the cool look of the larger computer, also the bungee mount option was great.
I'm dealing with what appears to be a cyst in my maxillary sinus at the moment (waiting for another MRI) which keeps causing me problems after diving, so I've only managed to get a couple of dives in with the G1 so far.
In terms of performance in the water, after glancing at both computers, the depth, NDL and temperature etc. are pretty much identical. The screen on the G1 is high contrast and despite looking like a late 90s calculator, is pretty easy to read under water, though not quite as sharp as the Teric. Note that I wear them on opposite wrists and the G1 is under my wetsuit in order to be able to track heart rate. As mentioned previously, beyond those initial dive values, the G1 falls a little short since it doesn't appear to offer any precise insight into things like surface GF or GF99, though it uses the same deco algorithm as the shearwater. There is an N2 loading bar on the left, though I don't find it too useful. Both computers are set to 35/85 GF.
I use my G1 as a backup computer and hence switch all the dive alerts / notifications off on it, however I noticed that unless I set it to dive mode before I descend, it does not log the GPS co-ordinates for the dive. A little annoying as I wanted it to be as hands off as possible due to simply being a backup, however I will have to remember to carry out that extra step after prepping the Teric.