You can compare the specifications via the following pages:
PicoScope 5203: http://www.picotech.com/discontinued/PicoScope5203.html
PicoScope 2208A: http://www.picotech.com/picoscope2200-specifications.html
The PicoScope 2208A has a small footprint relative to the PicoScope 5203 but one thing to note is that it does not have an external trigger inputs.
Although the maximum sampling rates are identical, the PicoScope 5203 has a large onboard buffer memory (32MS) compared to 48ks for the PicoScope 2208A, while in terms of bandwidth the PicoScope 5203 has a bandwdith of 250MHz versus 200MHz for the PicoScope 2208A.
The resolution (8 bits) is the same.
I hope this helps.