I've used both. Sybex tries to make the material more interesting. Cisco has all the information within their books. The main difference is read the CisoPress books after taking the exam and your afternoon will be..."That was exactly on the exam, alright I got it right, Nope got that one wrong, etc..." Cisco Exam = CiscoPress books, Questions are pulled from the books for the exams especially for the CCNA. Once you start pursuing the higher levels of Cisco Certs, more information will be needed from different sources. RFCs, White papaers, CCO, etc...This happens so Cisco can test your knowledge on a system and not just take the exam as found inside the published book.
thek25
CCNP, CISSP in progress...