Metrics on output using different settings, based on my hardware below.
Different bit rates causes different file sizes, but not any noticeable difference on my monitor.
The biggest difference comes from the amount of time it takes to compile with Hardware Acceleration (HA)
1h50m Video Source Sony AVCHD 1440x1080 Dolby Digital 5.1 and x.v. Color on in all cases
The first Bit rate is the setting and second is the overall bit rate.

Produce AVCHD 1440x1080 (24Mpbs) HA On MPEG-TS: 18.2GB, 3h, Bitrate variable 22.1/23.7Mbps, scan type interlaced
Produce AVCHD 1440x1080 HA On MPEG-TS: 12.9GB, 3h, Bitrate variable 15.5/16.8Mbps
Create/BD 1440x1080 HA On BDAV: 18.8GB, 4h, Bitrate variable 22.9/24.3Mbps, scan type interlaced
Create/BD 1440x1080 HA Off BDAV: 18.0GB, 9h25m, Bitrate 22Mbps/23.4Mbps, scan type MBAFF Windows 7 Ultimate 64bit
Velocity Micro
Intel Core 2 CPU 6700 @ 2.66GHz
RAM 6GB
NVIDIA GeForce 8800 GTS v258.96
ViewSonic VX2255wm-4 dual extended display
K-Lite 32bit & 64bit
1680x1050
Windows 7 Basic background no Aero
Hitachi 400gb system dr