Personally I prefer single level hutches, I've had double tier even triple tier ones in the past and gave up on them because my guinea pigs wouldn't use the ramps. I think it's better for mine to have one big space on a single level to run around rather than something stacked high. I don't like how ramps can take up space, can be steep or sometimes get in the way.
My hutches are pretty long, 8 footers and obviously it's not practical for everyone to have hutches that take up quite so much space which is why double tiers can be better. I don't know how much you are looking to spend but you could get a single tier 8ft hutch for less than £100 if you contact local carpenters/joiners etc. Mine are solid timber not plywood which means the cost is probably justified since they will last such a long time.
Just do whatever works best for you, if you think your piggies will take to a double tier hutch and you find one that looks like it will fit the bill then go for it!