Basically they both work your pec, but you use a different angle so it just works your muscle a lil different. Like illmatic said, Inclined benchpress is said to work your upper pec a lil more and your shoulders (depending on the degrees, there is a point where your shoulders obviously work harder than your pec) .....
It also possible to do benchpress with your head on the lowest point - that would work the lower part of your pec and is a nice option to mix things up every now and then.
Anyway, what should u use? Both! I'd suggest normal benchpress, then flies and then go back and do inclined benchpress. 3 exercices but you work you pec pretty much from all directions. Angles are important.
About the bicpes, of course there is a difference. To use the barbell is a nice exercice and indeed it safes a lil time, yet if you use both arms at the same time you might not be able 2 burn out your biceps 100%. You gotta remember the muscles in your arms are small muscles. I'd suggest to use the barbell and curl for your arms and afterwards, as second exercice, isolate your muscles --> do an other exercice where u work them seperatly. You'll realize that also here angles are important, that you can work your muscles way harder if you use different approaches. I quickly googled a link for concentration curls,
http://www.exrx.net/WeightExercises/Brachialis/DBConcentrationCurl.html
Well and yes, you need some more weight as you get stronger.
