Subtitler:Why do titles look correct in Subtitler but are not antialiased

Why do titles look correct in Subtitler, but are not antialiased and look jaggy in Photoshop and Final Cut Pro?

What you are seeing in Photoshop when you look at RGB only is the unmultiplied image. As quite a few NLE support premultiplied alpha, the RGB values are unmultiplied by the alpha value.
You will see that in the Preview application the antialiasing looks fine. In the compositing, when you set the alpha property right, the titles will look right.
For example in Final Cut Pro, if you select the clip in the sequence, check the menu Modify:Alpha Type. the alpha type you have now is probably Black. it should be Straight.
Select all subtitles and set Modify:Alpha Type:Straight.