There is no 'best', there never will be. It all depends on what you're doing, your skills, and your budget.
There are three basic directions you can head in: matrix, BSP, or .X. Each has it strengths and weaknesses. Using a matrix works best for rolling hills and open terrain. BSPs work best for interiors, but there are some issues with using them in DBP. Direct X models are easy to create and digest, but require more object management.
Of course, all of this can change when the next update comes out since TGC has been very busy with FPSC and the technology from that will trickle into DBP.
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TAZ