I use Dialer One and notice I have double the contacts since it displays them singularly (each phone number separately) for each contact listed. Two questions:
First question to you: are you using this on a stock Eris, or on a rooted Eris running a vanilla Android ROM? I ask only because I am not sure that Dialer One adds that much functionality that the stock Eris dialer has, though, of course, vanilla Android does not have the dial by name feature.
Anyway, moving on:
1) is there a setting that will allow "contacts" to show only one contact even though it has multiple numbers?
Ok, this does not happen to me. If I start typing "Julia" (coincidentally, the name of both my mother and mother-in-law), each contact comes up only once. Tap on that contact, and it shows me all of her numbers.
Are you sure that you just don't have duplicate contacts? Or, to ask another way, I have a single contact for my mother that has her home phone number and her cell phone number, rather than one contact with her home phone number and a second contact with her cell phone number. Which way are your contacts stored?
Are these Google contacts or phone contacts? If they are Google contacts, if you go to
http://contacts.google.com/ and then click "More", and then find & merge duplicates, does this help?
If they are phone contacts, you can go into one of the contacts, edit it, press menu and there should be a "Join" command. From there you can join it with all of the other contact records that are the same person to get a single contact for each person. (Well, you can also do this with Google contacts, but the procedure above is better.) Incidentally, this also works if you sync contacts with Facebook as well. This happens to me if the names are not spelled exactly the same way.
2) Which app is used when you sync contacts with Google? The "people" original app or dialer one?
Dialer One just uses the contact on your phone - it doesn't create a second set of contacts. So, it uses the ones in "People". Since you mention "People" it seems that you are running stock Eris, so that should answer my first question above. However, I still wonder what Dialer One adds that the stock Dialer cannot do?
I am trying not to have double contacts when I sync.
Well, see what I wrote above to help detect and merge duplicates if there are some.