Hi Rob,
Allow me to add to the confusion, or at least share what I've learnt about my machine. I've got a Gaggia Factory G106, which seems to be a copy of the higher priced la Pavoni Romantica 16 cup design in chrome. The boiler design is slightly different from the Europiccola and Professional models, but I haven't got a clue if this affects performance.
Personally speaking, the pressure gauge has been very useful. My machine, and I'm assuming the Pavoni Professional as well (despite the review below), has an easily adjustable pressure stat in the bottom of the base. Out of the box, my machine was set at 1.0 bar, which provided mind-blowing steam pressure, but was really too hot for pulling shots. I played with settings, and settled on .7 bar as the best balance between good temps for crema laden, best tasting shots, and still ample steam power. Have a look at this Canadian site's review and comparison of the larger Gaggia to the Professional. However, I'd read it with a grain of salt, as most of the text body sounds like an advertisement rather than an unbiased review. But in the last paragraph, they mention hands on tweaking, and being able to pull shot after shot without burning the espresso.
http://www.coffeecrew.com/content/view/33/28/
Yesterday I had visitors, and the first chance to try pulling shots for more than one person. I was able to pull four doubles back to back, and they were consistent in output, not a burnt flavour in the house. Advertised output is not realistic though, as this exhausted the boiler's water reserve with steaming and pulling water through the group for cleaning. The Canadian review also mentions that the larger boiler capacity provides more steaming reserve, but I don't know if this is true. The 1.6 liter boiler takes about 8 minutes to reach operating temperature, and because of the lower temp/pressure setting I need to initially draw about 150ml of water through the grouphead and portafilter to sufficiently warm up things. The Gaggias were discontinued some time last year, and some online sources were selling their stock for considerably lower prices than the Pavonis. If you can find a Gaggia lever priced below the Pavonis, I reckon that would be a good choice.
However, I would recommend reading through Paul L's posts in this forum, as he offers very logical assessments as to why the smaller model is a good choice if your usage is going to be limited to yourself and possibly another special someone

. And have a look at his link to his photos, and you'll see that he achieves spectacular results with the smaller model.
My final bit of advice: keep researching for concrete facts about the differences between the machines, and decide what factors are most important to you before you buy. I lucked out and just happened upon my machine at an estate auction for an unbelievable price, but I really didn't know much about lever machines before I bought it. Learn all you can, and then you will be equipped to make the best choice for your needs/wants.
Whew, all this writing has left me shattered mates!
Best of luck,
Hogfire