Node-Webkit should perform identically to Chrome.
You could always download our demo at http://www.airscapegame.com to see the performance of a platformer using node-webkit export for yourself.
So I just played the first six levels from this demo. That was some of the choppiest audio issues I've ever experienced with a game that wasn't run on an emulator and I frequently dealt with massive slowdowns for short periods of time. These are my specs.
Operating System
MS Windows 7 64-bit SP1
CPU
AMD Phenom II X2 550
Callisto 45nm Technology
RAM
4.00 GB Dual-Channel DDR2 401MHz (5-5-5-15)
Motherboard
Gigabyte Technology Co., Ltd. GA-MA790X-UD4P (Socket M2)
Graphics
W2361 (1920x1080@60Hz)
512MB GeForce GTS 250 (EVGA)
Hard Drives
977GB SAMSUNG SAMSUNG HD103UJ ATA Device (SATA)
Optical Drives
TSSTcorp CDDVDW SH-S223L ATA Device
Audio
ASUS Xonar DS Audio Device
I should not be having these type of problems with my machine for that type of game. Now I'm even more concerned about Construct 2's performance issues than I was before. I was learning toward using Construct 2, but now I'm not so sure because of how your game ran for me. Like your game's performance was so annoying that I'll never consider buying it unless those issues are resolved which is a shame because you have a really cool game.