I think we both used same, and 실례합니다 is fomal exprassion. You should say 실례합니다. also, you use 저기요 if you need some help or ask to some peoples, you should say 저기요~ it's same mean "Excusme" I wish it help you

If I were trying to pass through a group of people I think that using 실례합니다 would be better to use than 저기요. I would use 저기요 when I'm trying to get someone's attention. For example, if I trying to get a waiter's/waitress attention I would most likely use 저기요.