I always go for the convenient option. Buy garam masala and use it for all my cooking. But if I want to cook some exotic dishes like beef ullarthu, chicken roast or mutton roast, then I use ONLY home made garam masala for the bright spicy flavour... and YES, it makes all the difference.
Here's my garam masala recipe
Fennel seeds (saunf/sonp/perinjeerakam): 1/2 cup
Cinnamon stick- 1/4 cup
Cardamom- seeds of 8 cardamom
Star Anise- 4
Heat a nonstick pan and dry roast the ingredients (important-medium flame)till you get the aroma
Let it cool and grind it till it is powdered properly.
Store it in an airtight container.