Broadly speaking, conventional reels are designed to be mounted above your fishing rod, with the axis aligned perpendicular to the fishing rod. Spinning reels, on the other hand, are attached below the rod and the axis is somewhat parallel to the fishing rod.
The choice of whether to use conventional reels or spinning reels might be easy to make depending on the type of fishing planned. More often than not though, that choice is determined by the pros and cons of each type of reel on one hand, and the preference of the angler on the other hand.
Other factors that might weigh heavily on what type of reel to use include:
- How far you can cast with the reel
- The accuracy of your chosen reel
- The weather conditions
- Whether you need a lot of drag stopping power or not
Price consideration does not play such a big role in the choice of reel these days. With advancement in design, drag systems, and braided lines, the price range for all types can overlap quite easily. So it is now common to come across a conventional reel that is more expensive than a spinning reel. The reverse also holds true.