The old MacBook Pros have Firewire and Ethernet.
The new ones have neither, but have an extra Thunderbolt port which can be adapted to those.
The old MacBook Pros have mini-Toslink Audio input which supports RCA mini-jack line input 1/8th inch you might find on some microphones. The new ones only have direct line-in audio-input with no cable connection possible. Though USB is frequently adapted to audio input.
The old ones have built-in DVD/CD burner. The new ones you need an external one.
Are the higher screen resolution and higher battery life worthwhile sacrifices? That's really up to you.
The new power adapters only work with the newer Retina machines, though an adapter allows you to use the older adapters on Retina machines. Sadly vice versa isn't true. You can't use a new adapter on an old machine.
Some older machines may support 10.7.2 or later. The new ones only support 10.7.5 or later, and some may only support 10.8 or later. Look at the age of the operating system and the release date of the specs.