You can only VC EX3300 with same product. Same applies to EX2200. No mix and match for these product lines today. If you want a higher end core VC then you should probably be looking at a combunation of EX4600 and EX4300, but price is higher.
Other option is to VC, say a pair of EX4600s, and then create a LAG to your EX3300s. The difference will be need to manage as two different devices (2 different pairs of RE's). Bandwidth will be the same, as EX3300 VC has 10G max today anyway.