300m's about 48mmx15mm. If you are comfortable with Deep Sea, than weight is not a problem with either one. Besides, 300m has an compatible OEM bracelet, and 1000m only a nice silicon strap. 300m is a better desk diver.
on how would you use it. If you intend to wear it everyday, you'd better choose a 300m which is not too large and heavy for daily wearing. If you would like an ultimate tool watch for time to time wearing, then 1000m automatic ( SBDX014/013 ) would be the best choose in my opinion.