why? can I somehow sell them for btc and come out ahead of simply mining btc?
They're about neck and neck right now in terms of profitability per watt, however, the profitability of BTC for video cards will be expected to drop upon the introduction of ASIC miners. ASIC miners do not exist for litecoin's algorithm (which is designed to be more ASIC resistant than SHA256), so GPU mining LTC should remain profitable for some time.
Unlike SHA256, scrypt requires 8kb of L1 cache per process unit and as large as possible, as fast as possible RAM to store a constantly accessed buffer into. Hence, when ASICs are created for litecoin the gain in speed/watt may not even be on the order of a magnitude, whereas the gain in speed/watt in hashing SHA256 is about 100x (or two orders of magnitude).