Its simple really.
For the maximum amount of gain, you want a 5/8 wave antenna. Its hard to beat a Maco V58 for the price.
If you want the best of the best, without outrageous gain numbers, that does everything it claims, you want the I-10K.
http://www.a1antennas.com/
What makes the I-10K better than the Maco V58 (or any other 5/8 wave antenna ever made)? A LOWER LOSS FEEDPOINT! The more energy you get into the antenna, the more energy radiates off the antenna. The I-10K is also mechanically superior to any other antenna listed in this thread.
It still surprises me that people search out the Enforcer antenna and based on the price, thinks it is a great antenna. Its tunable at the factory, because its not easy to tune at home. The coil and tap design, besides being lossy, does not allow any simple adjustments. At the very least, the Maco's tap and length can both be adjusted for lowest SWR.