AC3 vs Dolby Surround compatible MP3

[StickHorsie]

Say there's this 3½ hour long DVD movie, of which I wanted to make a 2028 MB (1.98 GB) AVI.

Now I could have kept the 966 MB original AC3 audio, but that would've left only 1062 MB for the video part (including overhead), which isn't very much for 3½ hours.

So I converted the AC3 to a Dolby Surround compatible (dplii) 160 kbps VBR MP3, which was only 210 MB, which in turn left a LOT of extra available MBs for the video part (VERY big difference there).

Since I don't have mutant ears, this sounded just as good on my 2 speaker system, and since the MP3 is Dolby Surround compatible, I assume that friends with more advanced systems than mine would still get a surround signal, but (apart from not having separate center + LFE channels) would there be other real discernable differences?