I agree with Stripes. Since you mentioned optical, I assume you are more concerned with audio than video. It depends on what you want or value the most and, as mentioned, what your display's native res is. The two advantages for using HDMI would be having a one cable connection and you can take advantage of some of the high res audio tracks. Using optical will only give you the core DTS or DD track.
Not sure which Toshiba unit you have so can't say for sure on that one, but the Sony BD will decode True HD if you have the latest firmware and will send that PCM to the 2600 which will play it. Some folks claim they can't hear the difference in True HD and reg DD and some want the "best" whether they can or not. I suggest you try both and let your ears be your guide if you have both of the cables.
As mentioned, 1080i for video will be the best you will get out of the 2600 if you use HDMI. Then again, depending on your screen size and veiwing distance, some say they can't tell the diff in 1080p and 1080i, either.
Welcome to the forum, by the way!