Computers are fast but not yet even in the stupid class. 1 800 555-1212 and 800 555-1212 are different numbers. (It's like merging addresses with the same house number on 5th Ave., Fifth Ave., 5th Avenue and Fifth Avenue - those are 4 different addresses to a computer.)
The best computer for "about equal" is still the human brain.
If the numbers you enter in Outlook are going to be used by a human being or by a cellphone, always leave out the 1. A cellphone registered in and used in North America assumes the +1, so you're just wasting space putting it in. (The 1 means "North America" to the phone system.) If Outlook is going to be dialing a lanline phone, you could solve the problem by putting the 1 in all phone numbers. Or, if you're just syncing once, change them in the phone manually.