4GB or 8GB (for my situation...)

Question

First of all, before anyone says "double the memory for only $100!" I'd like to say this: I work about 15 hours a week for minimum wage (6.20), it'll be an epic battle to try to convince my parents to LET me buy the $500 4gb model.. let alone $600, and, most importantly, will i ever USE those extra 4gb?? I have a rough idea, but i'm still in the dark on this one.
I looked up 1GB of music, about 240 songs. I'd guess that I'd use that much maximum, maybe one day I'll reach 300 songs, but not in the near future. (about 1 GB used up)
I saw photos were about 15,000 photos to 1GB. I would guess that the most photos I'd have on iPhone at one time would be around 300 photos at the most. (1/50GB?? Correct me if I'm wrong on this one)
Movies- A side question. I have DVD's lying around. Could I put them in my laptop and somehow sync them to my iPhone via iTunes or another method??? If I CAN, I'd probably have up to 7 or 8 movies, about an hour and a half each. I have NO IDEA how much memory videos/movies take up. I don't plan on having TV episodes on my iPhone, unless I went out and bought a season of one show at most.
I plan on using my iPhone for all of my e-mail purposes (who wouldn't?)
I plan on having bookmarks for the internet browser (duh..)
My contacts list will only be about 50 people at most
I will add a couple of apps like an AIM-compatible app and some games
If I had to GUESS at how much memory I'd use, I'd say between 2 and 3 GB, but music is the only thing I have a solid grasp for memory-wise. Like I said, it'd probably take a miracle to convince my parents to let me buy one of these at 500... I really don't want to push it.

Answer 1

I have '301 songs' on my iPhone and it has 1.5Gb free - so starting with 3.5Gb (the available memory in a 4Gb model), that means that 300 tunes/podcasts plus my data, synced from the Mac, takes up 2Gb.
For my use, both intended and expected, the 4Gb model is fine, but if I had any wish to use it for video, I think it would prove inadequate without continually shuffling of content. A feature-length movie on my iPod is, for example, about 350Mb so planning on having those at your disposal would mean picking which ones you want at any time and removing some and replacing them with others perhaps.
It's all down to your intended use, but Allan is right - since you can't add to the memory, it's better to buy more than you think you need rather than less. Even more so in your situation perhaps where there's 'just' a $100 difference than for some others for whom selling a 4Gb model and buying an 8Gb one would perhaps not be a problem.
By the way, you could always 'save' that $100 by buying a refurbished 8Gb one for the same price as a new 4Gb. Just look for the special deals tab on the right of the Apple store on-line page.