A difficult question to answer. Generally, when an Arrancar releases their Zanpakuto, they usually gain an increase in their basic abilities, including speed and strength. However there are some exceptions: the first to consider is Zommari Leroux who seems to lose his legs when he releases. Another would be Aaroniero Arruruerie whose massive release form would seem to be unwieldy, but he may be able to make up for that with the various powers he acquired from the various Hollows he has eaten. Choe Neng Poww's released form is so massive and heavy that he is considerably slowed. And although it was never shown there is speculation that Ggio Vega's "power form" is slower then his regular release form.