Outside is cheaper and often freer. A roof shields paint, seals and cushions from sun and leaves. If the van sits for months, the hall often earns its keep.
State the type in your StorXL request. The yard answers with what it actually has.
English short take. The longer Dutch guide is on storxl.nl.
Caravanstalling 路 Amsterdam 路 Utrecht 路 Rotterdam 路 Kampen