Definitely polished nickel. It is so classy, good quality polished nickel has the warm glow of silver. It adds warmth to your space, chrome is bluish and rather cold.

Definitely, I agree, between those two choices you should go for polished nickel. It works much better with the surfaces you have, and it's also easier to keep it looking nice (imagine how often you would be wiping fingerprints off chrome pulls).

If you want to add sparkle, either get a sparkly accent or two (mixer, tea kettle, etc.) or consider some accent pulls--maybe the upper cabinets could have different pulls than the lower ones, pulls with more color and/or sparkle. Examples below.

Sparkly candy-apple red KitchenAid mixer (let this live on the counter and there's plenty of sparkle for ya--I've seen it in person, the paint is glittery like auto-body paint):
http://www.amazon.com/KitchenAid-KSM158GBCA-Anniversary-Limited-5-Quart/dp/B002JB1BRO

Sparkly glass pulls (clear or colors):
http://houseofantiquehardware.com/s.nl/sc.11/category.100/.f