The main difference between the 346 and the 34 is the 346 has a sugarscoop stern and superceded the 34 so will be younger. Otherwise the layout below is almost identical. Both designs were built by Marine Projects. (see a link to my example below)
Hi Chris, I've got a 34 Excel and my friend on the next mooring has a 346. They are very similar in many ways but the Excel has undoubtedly got more room inside. This is probably due to the higher freeboard which gives better headroom. I've not sailed the 346 but have absolutely no complaints about the Excel. The only issue I have had is with the lip seals on the rudder shaft which had to be replaced. I've had 2 seasons now and been across the Channel 4 times and to Scilly. The boat has easily coped with wind up to 45+ knots and been really comfortable in all conditions. I think Prouts only made about 20 or so 34 Excel models, mine is No 17. The 346 next to me is a bilger so he can go where we can't and rest on the sand sometimes but we tend to prefer marinas and harbours anyway so it suits us. Happy buying!!