I've just completed an Access to Science course. I did my A-levels 19 years ago so I can't give an opinion on which is better. I chose Access because it was taught in one academic year, and less expensive. If I complete an undergraduate degree, the Access fee will be written off.
It is quite intensive as you are being taught a mixture of AS and A2 but in half the time, 9-10 months. After an initial settling in period we had three, four assignments at a time, with a fortnight turn-around to the next three, four assignments etc. I didn't have a job during mine, but if you change your mind re working you will need to be incredibly organised.
Assignments were workbooks, tests, assessed lab practicals, assessed discussion, presentations, posters, leaflets, factsheets but no essays as such. As Hamo said, the grading criteria for assignments are included at the front of each assignment, just make sure you're answering the questions asked with refence to the grading criteria. If your presentation, spelling, grammar and syntax are good, and you include several quality references, then you can pick up distinction marks for quality alone.
The upside to continuous assessment was no final exams. The downside was feeling that I was learning just enough to get me through each assignment, learning for the test, so-to-speak. We moved from topic to topic so quickly that I am spending my summer refreshing myself on content I was taught within the last ten months. I was not as organised as I could (should) have been, so this may be more a reflection on my time-management skills.
I would recommend Access. It's a good course and my college taught it well, testing us rigorously and with variety. Whichever course you decide, good luck!