Who to get rec letters from?

[CSallday]

I am interested in a PhD in machine learning. Two of my rec letters will come from computer engineering professors who I did research with. The last one is up for debate. One option is with a professor who knows me well and whose class I TA'd many times working closely with the professor. The other is a professor in machine learning whose class I took and did really well in, but I don't otherwise have too much of a connection to. I am worried about having no rec letters from an AI/machine learning professor even though that's the field I wish to pursue.

[complexbongo]

I think this depends greatly.

 

Generally, I would say to definitely choose the professor you TA'd for, because he will speak genuinely about his experiences with you and his faith in you moving forward.

 

However, if the machine learning professor is a world-renowned researcher, then this might give you a huge boost in your application (given he writes a decent letter that doesn't sound generic). 

 

 

That said, my suggestion is that unless the ML professor is a big name guy, I would go with the professor you TA'd for -- he will write a great letter for you since he knows you well and you have worked hard for him. 

[PhDerp]

Most schools let you submit more than 3 letters of recommendation, they just require a minimum of 3.

 

So why not both?

[complexbongo]

Most schools let you submit more than 3 letters of recommendation, they just require a minimum of 3.

 

So why not both?

Also a valid point, +1. I would go with this unless the school says strictly 3 only. 

[DeleteMePlease]

You could also ask them if they are willing to write a strong letter.

(I think) I got a very good one from a prof I just took classes at and had no other connection to. Of course I had good marks in his classes and gave him a CV of me so he had something to write about.

[Icydubloon]

If you send 4, that increases the chance of one letter being generic or weak.