anther single hander question...

You can get a decent 600 for a

I think a musto is easier to sail than a 600 without the kite. It is easier to tack and gybe and pretty seakindly as well due to its length. Put the kite up and if you don't systemise the manouevres then yes you will struggle.

Get yourself a 600. You won't look back. I owned one for 4 years and it was the best thing that happened to my sailing. There's no question that it's a handful. Tacking the thing is notorious for a reason but there's simply nothing as rewarding as getting your maneoeuvres on a skiff down. If you do fancy racing, the fleet is resurgent. Get yourself on to the very active Facebook page. You'll find a bargain and a decent circuit. There should be at least 20 boats at the RS games in August. It's still one of the most exciting boats going if you can get used to its quirks. 

The 600 is a great boat. I had one for a bit, was just getting the hang of it when I went back to sailing 2-up.
You need to put the hours in.
Some coaching is very valuable, I don't know who is who in the class any more.
To some extent it depends where you sail, it's not an easy boat to short-tack up a narrow channel getting to our sailing area.
But It's very rewarding..
I was too old when I bought mine. 45? But I had trapezed all sorts of stuff before including a contender years back. I was also not very fit or healthy. It's not that hard to right, but 6 capsizes in a race in F4 when you're learning wears you down.
All worth it when it trucks past other boats with zero effort upwind.
If one comes your way at a bargain price, it won't be the worst thing you ever buy.
But, if you can find the cash, people I trust say the RS700 is easier to sail, and the MPS easier again.
A Contender is worth thinking about, if you sail somewhere with some decent breeze, but too many wednesday evening drifters ruined it for me.
I'm now Lasering one day a week, it's great but only as much fun as the people you race with.
My view is that learning any different boat is a plus.

There's a good reason 600's are a handful.. now I just happen to have a Laser EPS for sale..