Looking at getting a Cervelo R3. The last road bike I had was a Tarmac.

Does the Cervelo fit different than the Tarmac? Would I be safe getting the same size? I looked at specs on geometry but am not very familiar with what they mean.

Would you say they are comparable bikes or would I notice a difference between a Specialized Tarmac and Cervelo R3? There was something "off" with the Tarmac and I had 3 different fits. Could be I just am not comfortable on a road bike, started on a Tri bike and rarely road my Tarmac.