Vetteran I may be able to help with info on Ada. I live about 15 mi. from there.
Bars -- I'm not sure about the night life in either place (I'm not a night person). I know there are several small bars in and around Ada. I have no idea as to there quality sorry.
Not trying to get religious however if you attend church (and you can and still go to bars you just don't recognize fellow members there

) there are also about 80 churches in Ada.
Probable advantage of Ardmore is I-35. Also as Synopsis said it's about 30% larger so there are more businesses. I know there is a new large shopping center going in just off of I-35. However Ada also has a new shopping center going in although it's not near as far along nor does is look to be as large.
Crime -- My opinion on crime is that Ardmore probably has more but it is probably due to the larger size. Honestly Ada is not too bad, mostly drug problems like anywhere, very little violent crime but it does happen.
Internet -- As far as Internet in Ada goes both the local cable company (cable one) as well as the phone company (AT&T) offer high speed internet. There are also a couple of wireless companies but I don't hear good things about them. Don't know about Ardmore but I would guess it's about the same.
Water -- Ada gets it water from Byrd's Mill Spring so it's probably about the best water you can get. There is a lot of lime in it but it tases great. I don't know anything about Ardmore's water supply.
Roads -- Ada has done major improvements on it's streets recently. There are still some bad ones mostly in residential areas, but the City seems to be doing a good (although slow) job on fixing them. Highways into Ada are very good not much in the way of 4-lane but very good 2 lane for the most part. As far as Ardmore goes the roads seem to be in good shape but it might take you some time to figure them out. Some of them seem to be laid out as an afterthought.
Weather -- Ada usually gets the same storms Ardmore gets they just hit Ardmore first. They normally track on a path from Ardmore to Ada.
I hope that answers some of your questions at least about Ada. If you think of anything else just ask. I don't frequent this board often but I'll try to remember to check back for the next few days.
Oh one other thing. Ada is a very clickish place, although you can be accepted sometimes it can take a while.