CISCO 3750 VS 3560 What is the difference between them?

The main difference is that the Cisco Catalyst 3750 supports Cisco StackWise, i.e. creating one large virtual switch out of multiple chassis.  The 3650 has a “cluster” feature which while it sounds close, just means that you can control multiple switches from a single one.

The Cisco 3750 Series Catalyst v2 are next-generation energy-efficient Layer 3 Fast Ethernet stackable switches. Cisco 3750 Series switches support Cisco EnergyWise technology, which helps companies manage the power consumption of their network infrastructure and network-attached devices, thereby reducing their energy costs and carbon footprints.
The Cisco Catalyst 3750 v2 Series consumes less power than its predecessors and is the ideal access layer for enterprise, retail, and branch-office environments. It increases productivity and provides investment protection by helping enable a unified network for data, voice, and video.

Catalyst 3750 VS 3560

When it comes to the Cisco 3750E vs 3750X, The X offers what Cisco is calling StackPower, the ability to share power loads between multiple switches.  This is a beneficial feature when it comes to PoE+.  StackPower allows up to four members of the same StackWise group to combine their power supplies into one large virtual power supply.  It also allows some of the power supplies to be taken offline, increasing efficiency.

For building out small to medium offices these two features are quite valuable.  Start with one switch and add on with little to no disruption, while only using the power needed.

Here the Cisco 3750 information: http://www.3anetwork.com/cisco-catalyst-3750-switches-price_c41

Cisco 3750V2: http://www.3anetwork.com/cisco-ws-c3750v2-24ps-s-price_p109.html