Does 58mm make better espresso than 54mm?

Not on its own. A wider basket spreads the same dose into a shallower bed, which changes how water moves through it, but competent machines exist at both sizes. The accessory market is the real difference.

Can I use a 58mm tamper on a 57mm portafilter?

Usually yes -- Lelit's 57mm group is commonly used with 58mm tamping and distribution tools. Baskets are not interchangeable.

54mm vs 58mm portafilters

The portafilter is the handled basket holder you lock into the machine. Its diameter determines which baskets fit, which tampers fit, and which of the hundreds of aftermarket accessories are available to you.

51, 54 and 58mm at their true relative sizes. The difference in the cup is small. The difference in what you can buy afterwards is not: 58mm is the commercial standard, so baskets, tampers and distribution tools are abundant, while 51mm has a thin accessory market.

What changes in the cup

Very little, directly. A wider basket holds the same dose in a shallower, wider bed. That changes the geometry of how water passes through the coffee, and people argue about the consequences. What is not in dispute is that excellent espresso is made on both sizes every day.

If someone tells you 58mm tastes better, ask them what else was different.

What changes around it

This is the real story. 58mm is the size used by commercial machines, which means:

Baskets. Precision baskets from IMS, VST and others are made in 58mm first

and sometimes only.

Tampers and distribution tools. The 58mm market is enormous and competitive.

The 54mm market is smaller and more expensive per option.

Bottomless portafilters. The single most useful diagnostic tool in home

espresso — it shows you channelling as it happens — is easy to find in 58mm.

Resale and continuity. If you upgrade the machine and stay at 58mm, your

accessories move with you.

Who uses what

58mm: Gaggia Classic Pro, Breville Dual Boiler, Breville Oracle Jet, Profitec GO, Flair 58, and essentially every prosumer machine.

57mm: Lelit Anna. Lelit's own size; 58mm tamping and distribution tools generally fit, baskets do not.

54mm: most of Breville's Barista and Bambino ranges, including the Bambino, Bambino Plus, Barista Express and Barista Pro. The accessory market is smaller but perfectly adequate.

51mm and smaller: De'Longhi's entry range, including the Stilosa and Dedica. Here the thin accessory market is a genuine constraint, and it is one of the reasons those machines have a limited upgrade path.

How to weigh it

If you expect to keep this machine for two years and move on, portafilter size barely matters. If you expect to spend a decade improving one setup, 58mm gives you somewhere to go. That is why Preinfuse's upgrade-path rating counts it, and why a sub-54mm portafilter loses a point.