Porcelain is a tough tile which will not crack or break easily. they are very long lasting. vinyl is out dated and just doesn't look good. Your other option should be ceramic tiles. So it should be between ceramic and porcelain. I'd still recommend porcelain but ceramic is cheaper, that's the biggest advantage of ceramic. I bought these porcelain tiles two weeks ago, they look lovely. beautiful hexagon porcelain tiles

If considering wood you could get unfinished wood installed. Companies such as Wood Floor Accessories are a great supplier. Having it finished on site means a finish can be picked that works for your home. Each home has variables such as pets, different traffic and the owners desire to maintain the flooring or aversion to maintenance. Having wood finished on site has advantages. You can pick the highest quality product that works for your budget. The range of finishes available is quite wide. A professional company will try to understand your home and recommend the appropriate finish. They will also understand how easily the finish was can be renovated in the future. Amtico is an extremely robust product but being plastic, is just plastic flooring. It has its place, as does wood. In areas that have plenty of light surfaces, scratches show very easily on Amtico, Karndean etc. The manufacturers push a polishing maintenance product on consumers. However, this needs to be stripped and reapplied on a regular basis.

Ask your self if the kitchen is actually a good kitchen….. if you need a utility room next to the kitchen for additional refrigeration or storage or additional work surface then it’s not a good enough kitchen for you. Ideally the utility should be just a laundry room in which case it’s best near the bedrooms upstairs or at least near the bottom of the stairs.

I'd also be inclined to swap them as Jonathan suggested. Check fire regulations, as perhaps you do need to rotate the stairs to allow an open kitchen. (I'm in the Netherlands so can't advise on these.)