DL DVD vs. blu-ray

25gb, who needs it? isnt DL DVD big enough? normal DVDs sure are cheap and the capacity is big. A 4.7gb 0.20c DVD is 6.7 times bigger than a 0.12c 700mb CD-R. What are you planning to put on a 25gb disc? RAW files?
Many files stored means possible loss or damage to the disc will result in 25gb going kaput instead of just 4.78gb.

It’s called high definition. Suggest you read up on it. 2 million pixels per frame, vs 345,000 pixels on a DVD. Do the math on the required bit rates and you will understand the need for larger disc capacity.

I am talking about storage, not video quality. for the price of a blu-ray drive, I can get a 500gb external hdd.

But video quality is highly related to the amount of storage.

for the price of a blu-ray drive, I can get a 500gb external hdd.

Right now a blu-ray drive is still expensive for some. It will go down eventually.

It is true that most Blu-ray uses is for video/movies. But there are some businesses that use blu-ray for data storage as an cheaper alternative to tape backup solution.

Cheaper media is coming soon (LTH / HTL).