Some numbers and it's all about the numbers.
A group 29 MARINE/deep cycle (or just about any G-29 save Optima) is just over 100 Amp hours. about 20-25 usable before you damage the battery So you have about 40-50 Amp Hours of usable power
200 watts is about 20 amps by the time the inverter converts it.. But you likely won´t be using that much.
NOw a pair of GC-2 (Taller but you would need to shim them some side wise) hold 220 amp hours (About the same total amp hours) but you can use half or 110 of those because those are DEEP CYCLE batteris. that? over twice the usable watts. and a smaller price tag in most cases.