It comes down to which boot fits you best. Assuming both boots fit you equally well of the two boots you have chosen I would pick the Meindl Sedona Lady MFS GTX because it is smooth leather which is easier to clean and maintain than brushed nubuck and doesn't incorporate textile material down the sides of the tongue. It should be noted that Meindl lasts are normally wide fitting so may not fit/suit narrow feet.
Having said that brushed nubuck can easily be waxed (I have waxed the brushed nubuck models I have owned) and after a few coats you will end up with a smooth leather boot
but the Mammut Trovat Advanced High GTX also has textile material down the sides of the tongue which can be diffcult to clean and maintain and can wear out prematurely.
From a quick look online both boots are around £170-200 with a few examples available online in very limited sizes and availabilty at around £100.
If you want high quality and something that will last and your budget is not a problem I would suggest that you have a look at the following Altberg boots and add them to your list of possibles for comparison. Altberg are the only manufacturer to offer boots in 5 width fitting from extra wide to extra narrow and all Altberg boots can be resoled by the factory if and when the need arises.
3 Season Boots
Altberg Tethera Ladies 1252g/pair RRP £214.99 (standard last with 5 width fittings)
https://www.altberg.co.uk/product/the-tethera-ladies-boot-mto/Altberg Nordkapp Unisex 1460g/pair RRP £219.99 (A-Forme last with 1 medium width fitting)
https://www.altberg.co.uk/product/factory-stock-nordkapp/If the model of a boot made on the standard last doesn't quite fit or suit your particular foot shape and volume it's a fairly safe be that the boot made on the A-Forme last will.
Both of those boots listed above will be more than up to your needs and can easily cope with all the weather conditions and terrain the UK can throw at you including winter use with flexible crampons.
You can find your nearest stockist here
https://www.altberg.co.uk/stockists/ The ones to look for are the Premier Retailers with the red flags on the map who have been trained by Altberg staff and tend to carry a wider range of stock. NB You may need to travel quite some distance to get to your nearest Premier Retailer. Wherever you choose to go make sure you phone before you go so you don't waste time and money travelling to look at something that's not in stock.
Once you know which model boot you want and most importantly have been properly measured so you know the size and width fitting you require most of the models can be bought cheaper online than the RRP. Occasional second hand bargains also appear on eBay quite regularly.
If they are within a sensible travelling distance I would highly recommend a visit to Whalley Warm & Dry
https://www.whalleyoutdoor.co.uk/boot-fitting-service/ who are an Altberg Premier Retailer and I cannot recommend their boot fitting service highly enough. Customers travel from all over the country to use their boot fitting skills and services and are highly recommended by many other forum members. If you ever get up to the Lake District or Yorkshire Dales it's well worth making a detour for a boot fitting appointment.
Your high arch problem can be easily resolved by replacing the manufacturers cheap and nasty insoles with something like the Superfeet Green or high arch specific insoles available from companies such as Sidas.