I've used both products. Meguiar's is smoother and will give a better shine, while Autoglym will last longer but requires more effort. I'd suggest a thorough pre-wax prep if you were to use Autoglym. I'm sick of those products now. I've tried so many products and can't seem to find anything I like more than Zymol. If I were to buy a product other than Meguiars and Autoglym that you're comparing, I'd only by my true favorite...Zymol. Try the Zymol HD Cleanse followed by Titanium and then see how you feel about the other products.
By the way, in the UK Autoglym is sold in the discount stores for £5
If you want to be very serious about detailing products and tecniques, check out this site:
http://www.autopia.org/forum/