Which should I get? I'll be playing mostly in my room and don't need the 75W, but does it have any advantages over the 30W?
The 75W has the option to record via USB (digital). The 30W still has an analog headphone-out that you can use to record.
The 75w has 45 more watts than the 30.

If you're playing in your bedroom, there's absolutely no reason that you'd need a 75w amp.
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