I've got an Italian (Ferrari) floor corker & never had any problems with it at all. Well worth the $ I paid for it. I've heard the Portugese models have had some issues with the plastic iris scoring synthetic corks. The Italian model uses a brass iris & has no problems.
As for cappers, I use a wing capper for bottling 12 oz sample bottles. I decided to upgrade to a bench capper while bottling a 6 gallon batch of apfelwein in 12 oz bottles with a wing capper. I'll likely get the standard middle of the road model when I upgrade.
As for champagne bottling, I recently bottled 2 cases worth; it was pretty easy with the plastic stoppers & a rubber mallet. The wire twisting tool was a cinch to use too. Regards, GF.