No single best speaker here - they are built to different priorities, and the right one depends on your room, your sources and what you listen to.
| Area | Better | Why |
|---|
| Bass | evenly matched | Much the same reach (65Hz vs 65Hz). |
| Built-in power | evenly matched | Similar onboard amplification (25W vs 30W RMS). |
| Connections | evenly matched | The same set of inputs and streaming options. |
| Size | depends | Audioengine A2+ Wireless is easier to place; Mackie CR4-XBT is bigger, which usually goes with fuller bass. Your room decides. |
| Expandability | B | Audioengine A2+ Wireless: a sub output. Audioengine A2+ Wireless sits in a wider range (6 models), so a matched surround system is easier later. |
| Price | A | Mackie CR4-XBT is cheaper - $170 against $269, about 37% less. |
A Mackie CR4-XBT B Audioengine A2+ Wireless
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 speakers are judged; anything missing on either side is left out rather than guessed.
Which should you choose?
Audioengine A2+ Wireless is ahead, but only on 1 of the measured areas, and it costs about 58% more. That is a lot of money for a narrow margin on paper - Mackie CR4-XBT looks like the sensible buy unless something else about the Audioengine A2+ Wireless appeals to you. In a large or open-plan room, Mackie CR4-XBT has the cabinet volume to fill it more easily; in a small room, near a wall or at desk distance, Audioengine A2+ Wireless is the easier speaker to get right. Think about the whole system, not just the speakers: the roughly $99 saved by taking the cheaper pair would buy a subwoofer or a better amplifier, and either usually does more for the sound than the difference between these two.
And remember what a spec sheet cannot show: how each looks in your room and whether the finish suits it, what dealer support and warranty are like where you live, and how they actually sound to you. If you can hear them first - ideally with your own music - that will tell you more than any number above.