Always fished spinning reels, even for heavier duty techniques. I just recently bought a baitcaster but the brakes are garbage. The tension knob makes a difference but don't understand why there are both if they serve the same purpose

They don't serve the same purpose. What kind of reel did you buy?

 

The tension knob acts like a drag which applies even drag on the spool during the entire cast. You would normally set less drag for light baits and heavier drag for heavy baits. The drag on the spool helps prevent backlash during the cast.

 

The (usually numbered) brake knob is set to kick in when your bait begins to loose velocity towards the end of the cast when your spool is spinning faster than the velocity of the bait allows the line to feed out. It applies breaks to the spool to match the velocity of your bait to help prevent backlash towards the end of your cast..

Watch this. It answers all your questions (even the ones you haven't asked yet!):

 

 

First and foremost keep in mind that brakes on a bait caster are not intended to combat poor technique or eliminate the need to thumb the spool. 

1 hour ago, Delaware Valley Tackle said:

First and foremost keep in mind that brakes on a bait caster are not intended to combat poor technique or eliminate the need to thumb the spool. 

 

Well ~ I'm Hosed Then ..  ..  ..  ..  ..

A-Jay

Exactly. Learning to "feather " the spool will allow you to cast with very loose tension and virtually no brakes. Which equals extra casting distance. 

2 hours ago, Glenn said:

Watch this. It answers all your questions (even the ones you haven't asked yet!):

 

 

Thank you! This helped a ton. 

Also the tension adjustment has an effect on the handle turning resistance. Increase the tension and the handle takes more effort to turn, feels tight. I like my reels loose so keep spool tension to a minimum.

4 hours ago, Delaware Valley Tackle said:

First and foremost keep in mind that brakes on a bait caster are not intended to combat poor technique or eliminate the need to thumb the spool. 

They call me "Hitch hiker" cause I'm all thumbs

8 hours ago, MassBassin508 said:

They call me "Hitch hiker" cause I'm all thumbs

I'm all thumbs.  How come the names I get called aren't as nice?