So I've decided to do some extra work on theory to help my improv. But I don't want to neglect my ability to like sit down and write something. So the thought came to me that if you can improv good, you should be able to sit down and write good stuff...

True, false?
Do you like anime/manga?
PM me about buying the graphic novels I'm trying to sell
both. Improv helps you think of stuff quicker, but you still need to be able to wirte by actually puttng thought into what you're writing.
Ibanez RG42DX
Peavey Valveking100
Avatar 4x12 cabinet w/ Celestion Vintage 30's
Line 6 Spider 3
DOD Flanger
Ernie Ball Strings
Dean Edge 4
Peavey TNT 135
GHS Strings
some guys are good composers but are ****ty at improv......... so in a sense these bands "suck live" whereas bands with good improv skills can get a massiv rep from touring and wen u get the album it's nothing special........ then there's the guys who can do all of it......... respective examples are trivium, muse and old school ozzy osbourne.............<--mainly from drugs i assume
true, it helps phrasing massively, and it gets you to think of not just using one technique for a riff
Quote by beadhangingOne
There is no music but metal and muhammad is its prophet.
To quote Bill Evans...

"Jazz(improvization) is the process of making one minute's music in one minute's time, where as when you compose you can make one minute's music and take three months. That is the only basic difference."

If we are to believe Bill Evans, than the difference between improv and composition is simply a matter of degree. In answer to your question, if you can improvise, than yes you can compose, and probably better than you would be able to other wise.