Shell/OS for PSP 1.5

I hesitated about where I was gonna post this, but I hope I did the right thing when I posted it here. I'm getting my PSP back anyday now, since I borrowed it to a friend for the last two months or so. I remember reading abut shells for the PSP, with names like PSIX, PSP OS and Artillery and others I've forgotten about. I'm more or less wondering which one I should get, or if I should even get one at all. I have a few other questions, and if anyone would/could answer please give it a shot.

I go under the estimate that the PSP shells are running at 333mhz. Is that true? Does it drain more battery life than using no shell at all? Does the shell have support for say, xvid and divx, so I won't have to encode all my movies to mpeg4, or have to rely on several other homebrewapps for xvid and divx. I know that several shells support gif, jpg and png. Since I still have the 1.5 firmware I can't watch those without the need of a homebrew app. Can I listen to my mp3s at the same time I'm reading manga?

What other benefits is there for having a shell?

PSP-OSS/PSIX lets you change the cpu. Artillery runs at 222mhz. None of them let you view videos of any kind YET. You can play mp3's while looking at photos in all three (not sure about PSIX).

dj2005, do you recommend any of them?

I recommend PSP-OSS
1. It's Free.
2. Change your backgrounds.
3. Cool interface.
4. can play your homebrew and when you exit you return right back to the shell.

You have to pay 10usd to get the PRO version,and LITE sucks right now.You can't do anything with it.

Artillery is a good shell but still has a lot of bugs.I would keep my eye on this one in the future.