One is a streaming all-in-one and the other is an amplifier. Judge them on how many boxes you want and what you already own, not on the spec sheet alone.
| Area | Better | Why |
|---|
| Power | evenly matched | Effectively the same output - 150W against 150W into 8 ohms is under 1dB, which is not an audible difference in loudness. |
| Grip on hard loads | evenly matched | Both behave much the same into 4 ohms - output nearly doubles (300W and 300W). |
| Noise floor | evenly matched | Much the same signal-to-noise ratio (100dB vs 100dB). |
| Built-in DAC | B | Primare I35 Prisma has a DAC on board; the other needs an external one, which is another box, another power lead and another purchase. |
| Streaming | B | Only Primare I35 Prisma has AirPlay 2, Chromecast and Roon. |
| Analogue inputs | evenly matched | The same number of line-level inputs (5). |
| Room to grow | evenly matched | The same expansion options on both. |
| Price | A | Primare I35 costs less - $4,595 against $5,795 at list. |
| Watts per dollar | A | Primare I35 is the cheaper watt - about $31 per watt against $39. A blunt measure, and it says nothing about how either sounds, but it is the honest one for raw output. |
A Primare I35 B Primare I35 Prisma
depends neither is better in the abstract - it turns on your room, your system or how you will use them. Only specs published for both amplifiers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
The usual trade-off: Primare I35 Prisma measures better, Primare I35 costs about 21% less. With most speakers in most rooms that gap is smaller in practice than it looks here. If you already own a DAC or a streamer, the built-in one is money you are paying twice for, and Primare I35 becomes the more rational buy.
What a spec sheet cannot show: how either sounds with your speakers, how the controls feel day to day, and what the app is like to live with - which is where most all-in-one amplifiers are actually won or lost. Power figures are the manufacturers' own and are not measured to a common standard, so treat small differences as noise. If you can hear both, that will tell you more than any row above.