SQLite は非常に優れたデータベースだと思います。
恐らくは、MySQL よりも高速で、MySQL よりも簡単にデータベースを使用することができます。
データベース構造が単一であるのもバックアップのやり易さを考えるとメリットになるでしょう。
ここでは、SQLite3 の方を入れて見ます。

root@meckk:~# aptitude -y install sqlite3 
The following NEW packages will be installed:
  sqlite3
0 packages upgraded, 1 newly installed, 0 to remove and 0 not upgraded.
Need to get 101 kB of archives. After unpacking 176 kB will be used.
Get:1 http://ftp.riken.jp/Linux/debian/debian/ squeeze/main sqlite3 armel 3.7.3-1 [101 kB]
Fetched 101 kB in 1s (70.4 kB/s)
Selecting previously deselected package sqlite3.
(Reading database ... 15539 files and directories currently installed.)
Unpacking sqlite3 (from .../sqlite3_3.7.3-1_armel.deb) ...
Processing triggers for man-db ...
Setting up sqlite3 (3.7.3-1) ...

root@meckk:~#


root@meckk:~# apt-get -y install php5-sqlite 
Reading package lists... Done
Building dependency tree
Reading state information... Done
The following extra packages will be installed:
  libsqlite0
The following NEW packages will be installed:
  libsqlite0 php5-sqlite
0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded.
Need to get 223 kB of archives.
After this operation, 594 kB of additional disk space will be used.
Get:1 http://ftp.riken.jp/Linux/debian/debian/ squeeze/main libsqlite0 armel 2.8.17-6 [174 kB]
Get:2 http://security.debian.org/ squeeze/updates/main php5-sqlite armel 5.3.3-7+squeeze13 [49.4 kB]
Fetched 223 kB in 3s (68.4 kB/s)
Selecting previously deselected package libsqlite0.
(Reading database ... 15547 files and directories currently installed.)
Unpacking libsqlite0 (from .../libsqlite0_2.8.17-6_armel.deb) ...
Selecting previously deselected package php5-sqlite.
Unpacking php5-sqlite (from .../php5-sqlite_5.3.3-7+squeeze13_armel.deb) ...
Processing triggers for libapache2-mod-php5 ...
Reloading web server config: apache2.
Setting up libsqlite0 (2.8.17-6) ...
Setting up php5-sqlite (5.3.3-7+squeeze13) ...
root@meckk:~#


root@meckk:~# dpkg -l sqlite3 
Desired=Unknown/Install/Remove/Purge/Hold
| Status=Not/Inst/Conf-files/Unpacked/halF-conf/Half-inst/trig-aWait/Trig-pend
|/ Err?=(none)/Reinst-required (Status,Err: uppercase=bad)
||/ Name                      Version                   Description
+++-=========================-=========================-==================================================================
ii  sqlite3                   3.7.3-1                   A command line interface for SQLite 3
root@meckk:~#

インストールは簡単です。