It looks like the Breville you're looking at is a thermoblock machine as opposed to the Silvia which has heating elements and a boiler. Quality wise I don't think you can compare. The Silvia is an entry level machine that was orginally built as a thank you gift from commercial grade parts. Pressure to offer it for sale to the public got it on the market and it's been a consistent standard ever since. Gaggia's machines compete for top spot with the Silvia in the entry level market. There's a few other machines that are considered good starter machines but I've never run across the Breville being one of them.
The Silvia has no pressurized porta filter. It doesn't need one. The new models are a bit more expensive than the older ones because they're fitted now with adjustable over pressure valves that allow you to adjust the brew pressure. They've changed their thermostats as well for brew temps. I had a Silvia for almost a year. You need to be serious about espresso, I think, to appreciate her. You need a good grinder, good fresh roasted beans and an understanding and hand at preparing espresso. She's like a stripped down high performance sports car. Stiff suspension, manual steering and transmission, not at all built for comfort but in the right hands and with the right ingredients the performance can be exceptional. The Breville looks like it's built to be easy to use and easy on the pocket book but I wouldn't expect to get very close to what the Silvia is capable of. Look at Gaggia machines as an alternative.