For most jurisdictions, these two job titles are used to mean the same thing. These are the individuals who respond to the crime scene, take photographs, produce sketches, take measurements, take notes about the crime scene and the evidence, collect evidence, process for fingerprints, look for blood, hairs/fibers, footwear and tire track impressions, firearms evidence etc..... any type of evidence that would be found at a crimes scene, these individuals are trained to search for, recognize, preserve, process and collect. Depending on the size of the department they work for, this may be the only thing they do - respond to the crime scene for the purposes described above. In some departments, these professionals are also trained to process evidence in the laboratory for latent fingerprints; they may be trained to do fingerprint comparison/examination; they may be trained to perform footwear/tire track examinations; they may be trained to do blood spatter analysis; they may be trained to do firearms examination. Typically, the smaller the department, the more training in multiple disciplines a professional might receive. However, with larger departments, each professional is skilled at one discipline and usually works only in that discipline because of the needed knowledge and expertise and the amount of casework. For example, my forensics department has many separate disciplines and each section may have anywhere between 2 to 7 scientists; we have the Latent Print Examination Unit, Chemistry Unit, Trace Unit, Biology Unit, Photo Lab, Digital Evidence Unit, Evidence Processing/Footwear & Tire Examination Unit and a Firearms Unit. Within these units, the scientists only work within their specific area of expertise. These are the professionals that analyze any evidence collected by Officers, Detectives and our Crime Scene Unit. The Crime Scene Technicians do not analyze evidence within these fields.
Having said all of this, by starting out as a Crime Scene Technician/Investigator, you get a working knowledge of crimes scene, evidence handling and collection, rules of evidence, chain of custody etc. You also gain knowledge about all the various types of analysis that can be done to the evidence being collected. You can then go further and receive training in any discipline you become more interested in. Some jurisdictions may train you to perform these additional types of analysis while still working in a Crime Scene Technician capacity, or, you may move into the lab permanently to perform these types of jobs. Each and every jurisdiction/department is different depending on their size, needs and funding.
It sounds like you are wanting to work a job similar to what you see on CSI where the technicians work the crimes scenes, collect the evidence, analyze the evidence, talk to witnesses, interrogate and arrest suspects and work the case from start to finish in all capacities. I can tell you that this is not a true portrayal of forensic work. I do not know of any jurisdictions/departments that have positions like this. Most places will have the science professionals work the crimes scene....others who analyze the evidence...and Officer/Detectives who interview witness and interrogate/arrest suspects. It is a team effort between the scientists, police and states attorneys and no one can do it all themselves. Some officers/detectives do work in a crime scene technician capacity, however that is where it ends for them. They can be trained to do the crime scene work. Some of them are trained to do the analysis work inside of the lab. But if this is their function, they are not working on the investigation side and do not interview witness nor do they interrogate/arrest suspects.
Again, all jurisdictions/departments are different. I do suggest talking to as many professionals as you can. Ask your teachers/instructors for advice. Look at the geographical areas you are interested in working in and contact the departments in those areas to see how their labs are set up, what disciplines they have, what the qualifications are and ask to come in for a tour or an internship. Because everyone is different, there is not one size fits all job description that I can give you. Do your research and don't be afraid to ask questions!
I hope this helps! Good Luck!
Masters of Forensic Science/Crime Scene Investigation (George Washington University) 2003
Bachelors of Science in Criminal Justice/Medical Laboratory Technology (Old Dominion University) 2002
Forensic Analyst (Crime Scene, Evidence Processing, Footwear/Tire Track Examiner) 2004- present