I use double taper lines for almost all of my rods and I use many of them in the salt water also. I don't have any salt specific lines. However, a 5 weight may prove a bit light for salt water casting due to winds. This is not to say that it can't be done but that there are more appropriate rod / reel / line sets for salt water use.
Tell me what rod you own and that will be helpful also.
Where are you at? You might want to edit your details and add your location so we know when seeing a post where you are fishing. I used a 7'9" 5 weight for trout / spot and whatever I could reel in on the Eastern Shore VA. for a couple years. I even caught some blues with it but that was not quite as easy as trout. Flounder are a good tussle on a 5 weight too and they will grab up a streamer dragging along the bottom just fine.
Like I said I keep it simple and use DT lines for everything and your choice of reel will be fine.
Yes I'll update that. I'm in clearwater, Florida. I talked to a guy at a shop today and he told me that most guys around here use the weight forward, but I'm not really sure why that would be, mostly because I don't know what the benefits of either are anyway.
I catch a bunch of trout, ladyfish, flounder, etc here on light tackle spinning reels now and am looking forward to getting them on my fly.
I was going to say Weight Forward. That is my choice. I have to muscle DT too much. I like the longer thinner front taper on weight forward although after the first 30' it is all the same.
I prefer the GPX which is 1/2 weight heavier, but I also love the Windcutter II which is 1/2 line lighter at the front of the line. Smaller diameter to cut through the wind better. It truly is a wonderful line.
I recommend weight forward to new casters I work with, because I thing it is easier to cast. With sooo many different tapers these days and specialty lines, it is allot of, find one you like and stick with it.
Different casting strokes as well. I like Glass and Bamboo along with full flex Graphite, but I still prefer weight forward and that is my choice for what works best for me. I have a couple DT lines still and try them now and then, but, just not for me.
I do feel with you being a new comer, weight forward is the choice.
I agree with Joni. It's going to be hard enough fishing a 5wt in the salt (a bad idea IMO). Using a DT line would be a further handicap. DT lines tend to have a longer front taper and would make it even more difficult to cast salt water sized flies, especially in the wind.
If it were me and I was married to using a 5wt rod, I'd go with a 6wt weight forward line, and a cheap one too. ('cuz you're going to beat it up)
In other instances, I'd go with the DT for economic reasons (they're reversible) but not here.
I actually misspoke. Its a 5/6 wt rod, which I guess means either 5 or 6 wt line is suitable, and a friend of mine told me I'd be okay to put on 7wt line it. I dunno about that, but I'll at least do 6wt. And don't worry people use 5/6 all the time around here.