In general you want to use the least amount of product you can in a tank. You should really not need anything more than a dechlorinator in a well established tank. Water changes can take care of most problems. There are exceptions to this, such as needing to add minerals and good stuff back into RO water, using salt in a tank for various reasons, and using medications to deal with specific diseases.
There are times when using products may come in handy, such as using some stability to help in a mini cycle, but even in that case increasing water changes will usually help just fine.
In terms of brand preference it is a little bit of both of what you mentioned. Some folks just really like products they have always used and feel most comfortable with (I use NovAqua Plus as my dechlorinator, for example). And sometimes products are just not very good, such as Cycle which can actually deter the process of cycling. It just tanks paying attention and learning which is which
Most folks here will give you the pros and cons of any given product.