Both are very good, but be aware of the following:

Seating

BA seats are standard 2-3 CE seats on 319/320/321s

On AY, if you are on a 319/321, similar 2-3 seating, old cloth seats, slightly less comfortable than BA's but there's not much in it. If you are on a 320, then it's the new spacesaver seats in 3-3 config, and very tighly packed together. They have stopped selling the middle B and E seats in J, but unless you are in row 1, you will notice the difference in seat pitch. Row 1 (better on the DF seat, as the bulhead is further back) is good for legroom in these seats, anything further back is to be avoided at all costs.

Meals

BA is standard Band 3 grub - no starter, main course of pasta or curry, little pot of desert, cheese & biscuits with a few grapes.

AY catering is much better, nice big starter, large main course - eg meat or fish with vegetables, desert such as a mousse or apple pie.

Service

Very similar, although BA's can be a bit variable, AY's is always excellent. AY crew are very attentive and come frequently through the cabin offering drinks, bread, drinks, more drinks.

IFE

BA has the usual moving maps, telling you where Stansted isn't. AY has a moving map, some short documentary style programmes (with subtitles instead of sound) which are generally not worth watching. But the best bit about AY is the cameras which show on the monitors the views from the front of the plane of take off and approach/landing. If you know anyone in Hounslow, get them to wave as you come in to land.

Newspapers

BA (and AY) - usually lottery at LHR - will the bins be empty or not, so best borrow them from the lounge. At HEL, there's usually a choice of the Telegraph, the FT or the IHT on boarding. On AY they also come round in J offering the Telegraph, FT or IHT (or Finnish papers with unfeasible names).

Lounges/Terminals

Identical for both. Even though AY tell you use the Serviceair Lounge at T1, you can ignore that. HEL has the nice lounge right by gate 33, turn right for Emeralds, turn left for all other low-lives.


Check-In

For LHR-HEL, you can OLCI to a BA flight with a BA ticket, but not to a BA flight with an AY ticket (although the SSCI machines work for this) or an AY flight with a BA ticket.

For HEL-LHR there is no OLCI for BA flights. AY have an OLCI facility for AY flights, but it doesn't work if you have onward connections on your ticket.

Other Quirks

Remember you can travel to HEL via ARN (or via MAN) if you want more TPs.

Remember to use the BA flight code (for BA or AY operated flights) if you want tier bonuses and 50% cabin bonus, otherwise you'll only get 25% cabin bonus.

I tend to book whichever has the most suitable departure time, but definitely avoiding an AY 320 (unless you can nab seat 1D). The real choice is in the evening (1800) when the BA and AY planes go out a few minutes apart.