elite 4 hdi or elite 4x hdi?

[double p]

i'm trying to find a good fish finder that's not too expensive. i'm leaning towards the lowrance elite 4 hdi and the elite 4x hdi. looking at these two fish finders the only difference i can find is one has the micro sd card slot. is the sd card slot worth it? and what about the more expensive transducer? i'll be using it in the local bays and lakes, and eventually la jolla. so please let me know what you guys think of these units.