Nikon DL5100 Micro lens

Hi,

I'm thinking to buy a micro lens for my DL5100. Below are 2 lens which within my budget. Appreciate if anyone can give me some input/advice which lens should i buy
1. AF-S DX Micro-NIKKOR 40mm f/2.8G (USD279)
2. AF-S NIKKOR 50mm f/1.8G (USD219)

Another question is if i were to buy the AF-S NIKKOR 50mm f/1.8G which is in FX format, is there any problem with my DL5100 body which is on DX format? any effect on the photo quality?
Thanks in advance for the advice. Appreciate.