With a capacity of 2.3 GB, the largest DynaMO drive is also suited to larger amounts of data. But happily, it is also complete downwards compatible with all MO media between 128 MB and 2.3 GB - that also includes the 640. Thus the top model offers the greatest amount of flexibility.
Unlike the DynaMO 640U2, the 2300U2 works with an 8 MB cache; even the search time, at 19 ms according to the manufacturer, is once again shorter than with the 640 MB model. At 16 x 12 x 3.4 cm and about 630 grams, however, it is a good bit heavier - not a criterion to be overlooked in mobile use.
The DynaMO 2300U2 manages to take the lead in most benchmarks within its class. Compared with external hard drives, however, it has to throw in the towel pretty quickly. The manufacturer's promising claim for search time unfortunately doesn't translate to performance in practice: with about 45 ms access time, the DynaMO 640U2 Photo and the 2300U2 come out the same.