Every video format has pros and cons, but you have to understand first what video format your client can watch. On windows OS you can sure open an uncompressed AVI file, but this is not the best format to atach to an email, since it generates huge sized files.
You can easy create a DVX or XVID avi file: there is plenty of free applications that can do it automatically, but be sure that your client can open such formats.
There is even some free program to create FLASH videos. Flash videos can be compressed and are platform independent. Every good internet browser can play them, with the flash plugin installed.
In such cases, if my client has a minimum of computer knowdlege and skills, I suggest to install Sketchup. Then I send directly the .skp file. You save a lot of KB or MB and this is sure the best way to watch what you created. Moreover, your client can fully explore your creation.