Both do feature the new 14 Megapixel CCD sensor.
And A390 has Quick LiveView, while A290 has not.
Introductory prices in Sweden (approximately converted to Euro)
A290 + 18-55 mm 600 Euro
A390 + 18-55 mm 800 Euro
Common specs for both A290 and A390:
9 AF points
ISO up to 3200
Either Memory Stick or SD memory cards (no dual slot, but a single combo slot).
New Help Guide + Tip Function (very clever, says the magazine writer).