This is long and it is only my thoughts based on what I have read!!!
Disclaimer: I do not have an aftermarket tune. I am only stating my opinions based on what I have read on this site and the other in an attempt to help the OP with his decision. I have seen this exact post a number of times since joining this site and the other in MAY of 2012! Please don't flame me for this, instead, post your honest thoughts about your current tune or lack of one and your opinions of your tune!
Ultimately, I think that the "best tune" for your car really depends on your personal preferences, your desires with the car, and what you need based on the mods that you have.
I have labored over literally hundreds of threads on this site and that other forum, I have talked with people who have had a VMS tune, the Superchips tune, a Pat G tune, and a guy who has his G8 tuned locally by the GTO crowd with HP tuners, they all have things that they really like and things that they really dislike about their tunes. Okay, I take that back, the guy with the Pat G tune really had nothing bad to say about it.
From what I have found, Vector MS and Livernois will charge you once for their mail order tunes and then via email will work with you and update your tune with you as you mod your car. That ends, I believe once you add a cam... don't quote me on the cam part... just going off of memory and their website has all of that info. Both of those companies have package deals that really are a good deal for a mail order tune and a CAI. I think $700ish for the tune and the CAI (Rotofab?)... once again please don't quote me look at their websites they are site sponsors on here...
Pat G is out of TX and has his own website... you can google that.
I am pretty sure that most on here would tell you that with just a CAI and axlebacks or catbacks that the Cortex handheld is the best bang for your buck, but the tune files cannot be modded at all? what you get is what you get, and a lot of guys (search on here and you'll turn up a lot of threads with info) just aren't happy with the Cortex. Some guys are and you'll find those too.
If you have a local tuner you could take to them and have them throw it on a dyno or do a street tune, but that may be a one time deal also (most guys pay somewhere between $200 and $300 for a local guy to do the tune) but that also is a one time thing and if you change something on your car then you have to repay for a new tune. That is something that you would have to speak with your tuner about.
Your other option in the DIY route, which involves purchasing a softward suite like HP Tuners Pro or EFI live? This would allow you to make the changes to your tune as you see fit. Granted it would also allow you to royally mess up your car if you do not know what you are doing.
Ultimately, I think that the "best tune" for your car really depends on your personal preferences, your desires with the car, and what you need based on the mods that you have. There is no mogical answer to this question or I would already have an aftermarket tune on my car! Good luck man!