I worked a lot on ME3750..I can´t recommend this platform! The hardware and sw features are obsolete.
If you do not need MPLS, the ME3400E (E Series!!) supports features like "selective QinQ", wich could be very nice n an metro ethernet network.
You have only 1GE ports.
I think the ME3600X/3800X should be the choice. You have the features like 3400E and EVC support
The 3600X by default has enabled the two 10GE ports. The 3800X NO. Check the licensing model (also for scalabiliz, mpls) before you buy...
The features of the platforms are nearly the same.
The 3800X supports larger TCAM, more VRFs,ecc
I never used the 3600/3800 series.The platform is very new. But future proof
..or maybe a 6500 or 7600 platform (if you need port density)...?