For a quick delivery, I would go for any dealer who has your choice of vehicle actually ‘in stock’. It could just then be a matter of a few days before you can collect the car. You do lose flexibility on things like colour/options etc though.
In general, certain manufacturers who offer no, or only very limited options often ship over cars to European/UK compounds from where delivery can be relatively quick. These can be (but not limited to) Hyundai, Kia, Mazda, Mitsubishi, Suzuki etc. If you can be flexible on colour etc so much the better as you may not be waiting for the next ship to dock. However if a make/model is particularly sought-after there can be a long wait.
Where manufacturers permit you to spec various options and packs, these are invariably built to order. Hence can take many weeks or months if the model is very popular and if there is a back-log of orders stuck in the pipe-line.
Dave