In brief, you get the reliability and solid feel of a professional audio connector in a compact footprint (only slightly larger than a 3.5mm jack). The feel is similar to a very smooth, good quality, 1/4" jack, but requires slightly less insertion force due to smaller size (similar socket size to a banana), and unlike a 1/4" jack (too large), Bantams will fit on the 300 Series modules with a little modification. Bantam jacks are 3-conductor balanced compatible professional audio connectors with break contacts (useful for pre-patches).
Perhaps most importantly, unlike 3.5mm jacks, for which there is no standard and many variations exist, the shape and dimensions of Bantam jacks remain standard across the industry. This means no surprises due to tip shape variations (common amongst consumer audio 3.5mm plugs). Any Bantam plug will work in a Bantam jack.
Using Bantams not only means a more solid-feeling, robust, and longer-lasting connector that interfaces easily with studio patchbays, but as a bonus it also makes Wiard modules balanced-compatible. The signal outputs on the new boards are balanced impedance outputs, for best noise cancellation results when connected to a balanced input (though these can't be expected to drive exceedingly long cable lengths as the modules were not originally designed to do that). Inputs remain unbalanced, but in most cases you will have no problems connecting your balanced equipment directly to the module inputs, except in the case of a piece of equipment with a floating transformer output (these will need special handling—please ask).
These are top-quality professional jacks, but they don't cost the Earth! In fact, for new module orders (when Bantam jacks are specified up-front) there is no extra charge. In the past, Bantam jacks have tended to be prohibitively expensive, making them not a viable option for synthesizers for many people. Now there's no excuse for not having the best!
Existing 300 modules can be upgraded to Bantams too. DIY kits are available. Please email for information.