Lewisville is a very large city. Part of it is not great, but in TX, half of a city is usually not that great, and the other half is really nice.
Lewisville is a nice city with lots of shopping, places to eat, very nice people and schools are not great, but good. Some areas like Castle Hills have homes selling for 300K+ (cheap one). Some areas have homes selling for 100K+ (not so good). They have really nice apartment buildings by Vista Ridge area.
I used to live in Carrollton and I did really like. Be picky about your apartment building. In Carrollton, I recommend renting a house. There is a lot to do there as well. People are also very nice and both Lewisville and Carrollton are similar in the fact they are convenient for commuting. Both areas are huge so I would recommend you get a realtor if you plan to rent.
Carrollton has some really good schools. I would highly recommend staying either at Keller Springs or north of K.S.
Lewisville has a lot of good things, but I would recommend staying away from any apartments in the old downtown area which the original narrator refers to. Please do not think that all of Lewisville is bad. Parts of just about every city in Dallas area are better than some.
If you like water, may I also suggest renting in Grapevine? There is Lake Grapevine which is really nice as well. They have these great looking apartments just north of Grapevine Mills Mall called Verde Riverwalk. Lots of people have boats there. It's a gated apartment complex. I think they have lots of younger people there and I'm not sure how quiet it is (like any other apartment building). They have nice pools from the road!
Dallas area has a lot to offer. It took me about 8 months or so to adjust because it is so big
Good Luck. Please look around before making any decision.