The LPI website says the following:
1.14 I see there are two versions of the 101 exam - RPM and DPKG. What's this all about?
The LPI exam 101 has been re-published and is available with the following modules on package management as a small part of the exam.
* LPI-101-DPKG (this module offers questions on Debian's package management).
* LPI-101-RPM (this module offers questions on RedHat's package management).
The remainder of the exam is exactly the same.
You need to pass only one of these exams for the Level 1 certification, and along with a pass on exam 102 you will receive your Level 1 certification.
source:
http://lpi.org/en/faq1.html#1.14
I'm taking the test in August. Still haven't decided which to take but am strongly leaning toward the Debian version.