... most of the time Kotobukiya is a good choice when you are on a tight budget.. their products are good, but Hot Toys figures are better, imho.. also bear in mind that a Kotobukiya figure may be slightly smaller, always check the specification.
We sell both. I've reviewed the Koto one which you can see here.
I haven't got around to reviewing the Hot Toys one yet, but the paint job is very good, as is the pose.
Personally I think the Hot Toys one is a nicer pose. I'm not mad about the sea beneath the Koto one. I also think the Hot Toys one will hold value better than the Koto one.
Or you could go for the awesome Iron Man Mark XLII diets. This has just come into the UK and gives you fully possible and die-cast metal armour More info here.
If it were me, I'd go for the latter. More money, but totally worth it!