Transonic region- Straight wing
[ATTACH=CONFIG]250029[/ATTACH]

Swept wing will have lower overall wing wave drag- delay of drag rise:
[ATTACH=CONFIG]250030[/ATTACH]

Supersonic Vs Subsonic drag:
[ATTACH=CONFIG]250031[/ATTACH]

Note- While wing wave drag will be delayed and lower with a swept wing (and that is the largest contributor to wave drag), drag coefficient will still be much higher in the transonic. Beyond mach 1.2 Cd is relatively constant for most aircraft ( though drag will increase with speed)