Just a little general tip, try being a bit more specific in the thread title. "Need some advice" is a bit vague; "Need some advice with Terminator loadouts" or something along those lines is miles better
I don't know if Cataphracti terminators work differently to normal Terminators or not, or if that's the case in 30K, but I've always kitted my terminators out following these guidelines:
1) What does the rest of my army do?
2) What do I need from them?
3) Which weapons/ upgrades accomplish this best?
4) Can this role be covered better elsewhere?
5) Gear as needed.
Of course, magnetising them would be the best option. Then you never need to decide, per say, just swap them around as needed. Assuming you don't have or don't want to magnetise (like me), then we'll have to do this another way.
Ok, first, what's the rest of your army like? Terminators generally have a nice selection of wargear and are fairly flexible. You can use them to fill whatever gaps are in your army. (Before people get into competitiveness, we're talking about Terminators and 1K sons, alright? Not exactly Triptide, and it doesn't need to be.)
Generally, Terminators come in either shooty or assault flavours. Take
TH/
SS combos for a strong bully unit, while
SB/
PFs with a
CML brings ranged pain. Playing Chaos is a slightly different matter, though it follows roughly the same guidelines.
For Chaos, you have the option of mixing close combat and ranged weapons. However, I'd be cautious with this. mainly because the Chaos weapons... just suck, frankly. I'd leave the Reaper
AC at home, if you like it the Heavy flamer might be worth it. However, they're comparatively cheap and come with a power weapon base. These are good for really bullying
MEQs and so on, but throwing a lot of weapons upgrades onto Chaos Terminators gets expensive quickly, and isn't really worth it
IMO. They also don't have access to
SS, so there's that.
Terminators are naturally durable. They can be particularly hurty, or throw out some support fire. Just remember they're not a one (five) man army, and won't be able to hold up unsupported.