What is the best way to make my case to my Manager to select me to go to the conference?
The issue here is the business has a very understandable need to ensure that the paper is presented well.
Note that just because you did the work, doesn't mean you are the best equipped to present it. That is the reality of the situation.
If it's your company policy to only send one person, you can suggest you finding your own accommodation, and own flights, and ask the company to allow you to co-present the paper with your manager.
Other than that, it's their business call on who to send. In the future, if this matters a lot to you, you should make sure your employment conditions mandate that you are the one to present papers you work on.
The quality of the presentation is IMHO a very weak argument and is used by your manager as it can't be quantified, so it's hard for you to rebut it.
It's a tech/scientific conference and not a sales pitch, so great rhetoric abilities do not matter as much as the ability to answer questions directly after the talk or during the coffee breaks. Would you (or anyone higher in your company) refuse to work with a researcher just because she stuttered during the presentation? (I even was at a conference once in which a Japanese researcher used a text-to-speech program for his 10min talk and no one really cared)
Only a small part of the conference is the presentation itself (which can be rather short), more important are the individual discussions. Your manager most likely won't be able to discuss the paper in depth.
But as I spent almost an year and a half developing and writing the paper
That's a lot of time spent in writing down, its natural for you to be dejected, given that its also been noted that 60% of it is your contribution, while manager is 10%
It seems that the manager is trying to take credit for your work by selfishly taking this opportunity to present for himself, rather than you or the senior employee.
While its true the company owns the IP etc, and can choose to send any of its employee to represent itself, this is one of those rare situations where you should touch base with your skip level manager.
strongly desire to change work or pursue further studies.
Winner never quits, and quitter never wins. Don't go down without highlighting the wrong here, as the manager may try same tactics at a different time for a different project as well.
Objectively state the facts, feelings regarding the matter to your skip level manager:
- You contributed the most to the paper
- The person being sent contributed least to the paper
- You feel dejected by the current decision
- Is there any way the current decision can be altered to send you
- If the aim is to send someone senior who can represent the company, then the better choice is the senior employee and not the manager, for reasons of technical depth.
FWIW, if you lack in presentation skill, a good manager should have taken this as an opportunity to improve these skills of yours, not hog all the attention for himself.