Big red : Definitely seems to favour marines. There's not many good hive locations, and a few hive locations are outright bad due to easy entrapment, especially on high pop. (lambda, viro) The caves are rather straightforward for the largest chunk. It's just two big vertical tunnels with a few connectors, and they're rather wide and open in many areas, allowing for shooting xenos in a barrel. This also makes it harder and more time intensive to sticky up. With only a few entrances to the caves, of which two are close together. (eta, filtration) You can easily barricade in the xenos.
ice : Definite xeno favor. The fact there's two z-levels only accessible by a small lot of marines at times, with long winding tunnels that are easily stickies, and flankable. With the flanks being mostly 2x2 tunnels even easier to sticky. The size of the map also gives xenos extra time, and there's a million hive locations. On top of all that, snow takes longer for marines to clear, affects marines more harshly, and if you loose your helmet in some god forsaken corner of the map, you might as well freeze to death. There's many caves systems above ground too, that are nearly impossible to flank. Such as the one at excavations.
lv : Probably the most balanced map in my opinion. It has its flaws yes, but the river is unweedable, and marines aren't as disadvantaged pushing into it as xenos are, seeing as they can abuse range to cross it. The open areas allow for extensive use of cas, OB. The only strength for xenos here being the extensive, humongous and complex cave system. They can hide anywhere, and run the marines around in circles for eternity whilst picking them off. Many intermediate tunnels are a lot smaller and tighter too, allowing for easy sticky for drones and hivelords alike. The fog prevents rush, and most of the time the fog holes can provide as much of a death trap to marines, as a benefit. They're also easily held with a boiler and a crusher.
prison : This one can go either side. The distance between dropship and hive is tiny, yes. And they can easily flank up to three sides as once in a big pincer. But xenos have the easiest time ever stickying everything up. You can just plant a whole load of sticky, and hold marines at the countless tight chokes, namely being 2X2 hallways. Especially with crushers this one can become a cakewalk for benos. Marines do have the issue of getting lost or scattering, especially once they reach the open area of civ. Which benefits them by nature.