If cost is not an issue an implant is better but there are many factors that will decide which is best for you.
To do an implant you need sufficient bone height and width.
If you are considering an implant to replace a tooth that was extracted years ago it may not be possible because:
Insufficient volume of bone
Over eruption of the opposing tooth (insufficient vertical height to place a crown)
Significant tipping of adjacent teeth
Poor amount of keratinized gingival tissue
If any of the above apply to your case, you may need advance treatment to prepare the site for the implant.
These include bone grafts, gum grafts, braces, restorative treatment. In some cases, an implant is not possible at all.
Indication for a bridge
Many insurances will cover part of the expense of a bridge while most insurances do not cover cost of implants (this may change in future).
The overall cost of a bridge is generally lower. The main factors to choose a bridge over an implant:
If the adjacent teeth are weak or need a crown
If you are not happy with the adjacent teeth esthetics
Implant is not possible
Bridges are difficult to clean, it is hard to access the underside of a bridge, especially if it’s at the back.
Bridges and implants will not get cavities because they are inorganic but for a bridge the tooth structure below the bridge can get new cavities.
Both implants and bridges can be lost to gum disease. Due to the anatomy, it is even more important to have regular maintenance as they are more prone to gum disease.