Model Railroading > 11mmx15mm ESU Sugarcubes or TDS Mini?

I have read a number of positive reviews for the newer sugarcube speakers so i have picked some differentones up to try out. Unfortunately i have gotten some differing advise so here is my question. I am planning to install a few tsunami econami and one tsunami decoders in some older atlas locos. Two older atlas master gp40/gp38 style locos with no provisioning for sound and an atlas classic rs1. My question is whether to install dual ESU 11mm × 15mm sugarcubes in the cabs or a single tds mini sugarcube.Which setup will provide better sound assuming nice airtight fits in their enclosures? The second question is how to wire them if the dual speaker setup is prefered. In series or parallel? Thanks again!
MT