Being fairly new myself, most of my reading on the subject seems to say that hairgrass is easier then baby tears (needs more CO2, which as I have Excel and not pressurized was an concern for me). I have had success with the dwarf hairgrass and I may try some baby tears in the future.
What lighting do you have already? Or are you planning to purchase some?
Personally, I would go with Dwarf Hairgrass Bellem if you can find it - I've been reading great things about it staying at about 2" tall and making a great foreground plant.