The first is a small 20cm high simple stick aerial, costing a few pounds. This was found to give adequate reception of (16QAM-mode) Freeview channels in strong signal areas, especially outside.
However, unless it can be placed in direct sight of the transmitter an only unsatisfactory signal can be received.
The second form of aerial is of the Yagi design of around 30cm length, costing around 10.
This aerial was slightly better than the simple stick design, largely because it can be directed to point at the transmitter and be positioned horizontally or vertically as required.
However, in poor signal areas the 64QAM channels were not received, and the aerial required good placement to get an uninterrupted Freeview signal.
Indoor Panel aerial
This was found to have around the same reception quality as the Indoor Yagi type, and cost around the same.
Indoor digital aerial with booster
Costing 25-30, the improvement of the signal provided by a modern internal TV aerial. Typically able to boost the signal by 36dB, this type of aerial when well positioned provided stable, uninterrupted Freeview reception on all channels.
Gui: Look at the digitaluk and terrain links below your question - your 22km from Black Hill. Thats not bad, but its an indoor aerial, which are normally pretty rubbish.
Indoor aerials work as well as they can - but at least try to get it as high as possible, and point it in the right direction. Then try tuning in the TV. Frankly, it might be OK, but if you can ask a neighbour to borrow their aerial for 10min while you tune it in, your better off than using the portable one initially.