Relevant Research Studies:

1) Maximal Strength Performance and Muscle Activation for the Bench Press and Triceps Extension Exercises Adopting Dumbbell, Barbell, and Machine Modalities Over Multiple Sets

2) A comparison of muscle activity and 1-RM strength of three chest-press exercises with different stability requirements

3) Narrative review of injuries in powerlifting with special reference to their association to the squat, bench press and deadlift

Relevant Dr. Gains YouTube Videos:

1) BEFORE YOU BENCH PRESS, Understand the Anatomy Behind it! (Incline, Decline, Close Grip, Wide, Form)

2) By popular demand - the free weight & bodyweight alternatives to the Inner Chest Squeeze Press! (shows the dumbbell "squeeze press" variation mentioned above)

Relevant Dr. Gains Workout Programs:

1) Hypertrophy Series Total Chest Program

Summary:

For this week's tip I'm going to give you 4 reasons why bench pressing with dumbbells is better for you than benching with a barbell.
1. First, Dumbbells have much higher stability requirements through every phase of the bench press motion, engaging all the stabilizing & synergistic muscles much more (that includes the upper and lower chest (aka clavicular and costal heads of pec major), the pectoralis minor, both biceps heads, the anterior deltoid, and the serratus anterior).
2. Second, Dumbbells have much greater versatility, giving you the ability to alter the press type and angles of resistance instantly - even mid-rep - changing how the target muscles are worked without having to pause and re-adjust (examples are wide vs close grip presses... pronated vs neutral vs supinated press... etc.). That versatility also allows you to do press variations that aren't even possible with a barbell! (such as the twisting press, or the squeeze press, where you squeeze the dumbbells together while you press out.)
3. Third, Dumbbells provide complete freedom of rotation in the wrists and shoulders, making you much less susceptible to injury compared to a barbell which locks your joints in place.
4. And fourth, Dumbbells give you the ability to perform the bench press unilaterally, or one side at a time, which opens the door to many benefits that only come from unilateral training, which I discussed in the previous podcast episode.
Now, I'm NOT saying that you shoulder never do barbell bench press... variety is key and the barbell press has its place. For example, it's better at targeting the triceps. What I AM saying is that if you had to choose between the two... the dumbell press is better! And you definitely should not be exclusively using a barbell.
Application, use dumbbells for the majority of your bench press exercises!