The long load up time isn't because of your hard drive...
It's because of it connecting to the internet and downloading the data which is displayed on the dashboard.
The last few updates have increased the amount of data which is downloaded and displayed on the dashboard, including video adverts.
If you turn of your router and then try turning on your Xbox, it will take less than 20% of the previous time.
In short, It's because of the dashboard updates, increasing how much data your Xbox downloads from the internet. I'd choose Xbox Live over a fast Xbox any day.