In metal it is not uncommon to use slightly heavier strings to facilitate dropped turnings which tends to give a somewhat darker and heavier sound to riffs. Equally fairly light top strings may be preferred for playing lead runs.
Having said that it is not unusual to see two guitarists in the same band with vastly different setups.
Nickel wound strings can add a bit of brightness which helps mitigate the muddy sound you can get from very low tunings.
As a very general rule of thumb heavier strings will give a more meaty sound while lighter ones make fast, precise playing easier so there is some compromise. This is one of the reasons why 7 string guitars are used by some bands.
Having said that string gauge is as much about playing style and feel as tone so it is worth trying a few different sets and see what works for you and it's not something you need to worry about a lot. Both brands you mention in the question are pretty standard for metal.
Thrash and related genres tend to have a mix of quiet bass heavy guitar riffs and technical solos which need to cut through the rest of the mix, although these will often be handles by tow guitarists with different setups, or at least some means to radically change tone on the fly.
It is also worth mentioning that frequency control is often at least as important as outright distortion in this type of metal so a good parametric or graphic EQ pedal may help a lot in getting the sound you want. Equally there are a ton of distortion pedals which are aimed at getting precisely this sort of sound and will often have some sort of parametric EQ in the form of a 'presence' and/or tone knob. These are often the easiest way to get a decent metal. You will never get the full punch of a big 4 speaker cabinet from a practice amp whatever you do but in most practice situations this isn't achievable anyway.